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Are you saying that all your pages have a canoncial pointing to your home-page? If so, then this is not good. Having distinct canonicals for different content is fine.

If you feel that some pages should not be crawled/indexed then rather use noindex/nofollow instead of pointing the canoncial to some other page.

Don't look at Alexa, especially if the website is not certified (i.e. has the Alexa tracking code installed). Even if a site is certified and has the tracking code installed, the traffic (both PV and visitors) is hugely underreported.

Almost all their stats are still some guesswork and fluctuate. Remember that Alexa will only track traffic if the toolbar is installed and it will use the JS tracking code to for additional metrics. You will typically find that only techies will run Alexa.

I would do perhaps competitive comparisons (if this is what you are looking for) with Google Trends, SeoMoz or any of the other tools, but in most cases it will still be guess work as your competitors will not openly share information. Another means is Google Adwords.

I consider Alexa a nice "vanity" rank and good for marketing purposes - i.e. "We are #5 on Alexa" - it means really nothing and has no impact on PVs, revenue etc.

I would go through this page first: http://support.google.com/webmasters/bin/answer.py?hl=en&answer=1093493 and then follow the instructions for implementing hproduct here: http://support.google.com/webmasters/bin/answer.py?hl=en&answer=146750#usage

Before you take your pages live, use the Richnsippets tool to test your markup: http://www.google.com/webmasters/tools/richsnippets

Make sure that you include category breadcrumbs in your product pages. The product markup and offer-markup is obvious and quite easy. If your site offers reviews on products, use the hreview tags as well - this will give you great exposure.

Be aware, that Google is quite difficult when it comes to "Your markup contains hidden data" - one example is if your price tag for example looks like this, Google will reject it: $100.50

Is the intention to eventually get rid of the old domain/brand (provided that the new one is successful)?

Duplicating a domain would mean that you would pay extra for PPC (driving different brand terms) and would also mean that the reskinning would include some brand-term landing pages.

I don't think your new site will take off from an SEO perspective - especially considering that it will take about 4-8 weeks for the index to properly build out and you will only know about any duplicate content issues after it happened.

I think "trying out a new brand" is a bit dangerous, by just duplicating content on another domain and slapping a new skin on it. Unless of course the current domain does not have much SEO value with regards to branded keywords.

Depending on the number of products I think it would be better to pull up the new domain with a set of landing pages (preferably covering some of the most revenue-driving and least revenue-driving products) and a set of product pages with canonicals to the new domain and sitemap for the selected set of products and then setup PPC and funnels and do a side-by-side comparison.

If the new domain/SERPs/conversion performs better, 301 the old domain to the new one and move your products over. Anything else feels like being half-pregnant

I personally would update your robots.txt and then submit a sitemap with the URLs in question via GWMT - this will result in your pages being crawled very quickly (within 48 hours) and then dropped out.

I would also look at either using 301's if you see link-juice from those URLs or using 404s/410s.

I personally found that resubmitting takes longer than pushing an updated sitemap.

I would carefully monitor the reputation of the IP as well as the IP-range (and even the ASN) the IP falls within. If any of those loose reputation - for example if one of your 80 sites hosts a trojan, all your 80 sites will be flagged.

I personally would only host domains and subdomains on the same IP but would not share an IP with multiple domains.

I have seen several sites completely die due to IP reputation issues.

How do you deal with DMCA takedown notices related to product descriptions? With Google it is simple enough for any person to submit a DMCA takedown notice irrespective if the owner holds right to the content.

One such example is this http://www.chillingeffects.org/notice.cgi?sID=1012391\. Although Google dealt in that particular case properly (and did not remove content), we find that nowadays more and more competitors use the DMCA takedowns as an easy way to de-index competitive content.

Since the person registering the DMCA takedown does not require to provide any proof of copyright, de-indexing happens quite quickly.

Try this URL: http://www.google.com/transparencyreport/removals/copyright/domains/mydomain.com/ (replace your domain) to see if you have been affected.

I would like your opinion if you have been affected by takedowns on product descriptions - in my mind if product descriptions are informative and relate to the characteristics of the product then takedowns should be denied.

I would also exclude them via robots.txt and then push through a sitemap with your static content to "nudge" Google to recrawl your content (and hopefully drop the other pages off quickly over time).

You could face the risk if your sites are interlinked and a manual review flags the sites as similar and demotes some. I think this is a very rare case and it will be unlikely that it could happen. Just remember, Google has a better understanding of link-graphs then any tool available. I have seen some sites drop due to a manual review (the demotion was not because of same UI though).

I honestly would not worry too much about it as long as your copy, brand, keywords and onpage SEO differs.

This is already happening - do a search for "google manual review" and have a look at the manual review process. Google currently employs companies to perform manual website reviews based on search terms to classify web-sites.

So although you have the same template, different content and websites, the danger is that your sites from a link-building perspective interlink and a manual review might demote all of them.

Chances are slim as others said, but certainly possible.

It's bad to have redirects - especially when all your content does a 301. Why can't you sort this out via rewrite rules or through your system directly?

Sida, what I meant is that I use the Google Webmaster Tool function "Fetch as Google" only as a diagnostic function to see how GoogleBot receives a request from my website.

It seems that people fetch URLs via the GWMT "Fetch as Google" and then use the function to submit it to the index. I find that not a good idea as any new content should either be discoverable (via SEO) or should be submitted to Google automatically via a sitemap (hinted in robots.txt)

I hazard to say that if the new product was in the sitemap it would have also appears in the SERPs. We submit sitemaps every day and products are in the index within hours.

I guess the GWMT manual submission is okay if you need to manually fix some pages, but then it asks the question, how your SEO efforts could not make those visible to bots (via link structure or sitemaps).