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There's an SEO I know who does nothing but buy expired domains and 301 them to his site. He claims excellent return on his investments in these older domains in terms of boosting his domains that he redirects to. So 301-ing a domain is worthwhile.

Depends on why the subdomains exist. If they're all carbon copies you might have an issue on your hands. If they're just various content, I wouldn't worry about it. Incidentally, some hosting programs (like Plesk, cPanel, etc.) will create a specific set of DNS entries for you automatically if you're not careful so that could be the source of some of this mess.

Should you consolidate domains? That depends. Are any of these subdomains penalized? Are they ranking better than your root site? Are they getting traffic? I would do your homework before consolidating. In some cases it might be better to just turn them off.

I would highly recommend you run your site through SSL Labs tool. It should help you identify any problems with your SSL install.

Also, make sure that you're loading GA in a secure manner. If it's not loaded securely and someone says not to load insecure assets then it won't show up.

The only caveat I would offer is to make sure you don't run afoul of any trademarks. You can do organic SEO all day long (falls under fair use) but if you run PPC with their trademark inside, they can request Google remove that ad (I know because I watchdog our brand the same way).

I would include a disclaimer on your site that you are not affiliated with Brand Name company and that their name is trademarked. Beyond that, write some good content to explain that Brand Name doesn't sell the product anymore, but you do. Would be useful information for potential clients. I know I like finding pages that explain what happened to a market segment I pay attention to (i.e. they left the market, went bankrupt, etc).

Not really. As big as this site sounds, attempting to do so would probably pose a security risk to your website (as an IT professional I can think of a few ways this could work, but all involve exposing the main server in ways I would cringe at). The subdomain has the fewest questions overall.

It's ironic you're asking that today. Search Engine land has an excellent article on just that

First click free: We’ve worked with subscription-based news services to arrange that the very first article seen by a Google News user (identifiable by referrer) doesn’t require a subscription. Although this first article can be seen without subscribing, any further clicks on the article page will prompt the user to log-in or subscribe to the news site….

It is possible to limit the number of free articles that a Google News reader can access via First Click Free. A user coming from the domain [.google.] must be able to see a minimum of 5 articles per day. This practice is described as “metering” the user: when the user has clicked on too many of a publisher’s articles from Google News, the meter for freely accessible articles on that site is exhausted.

If your site meters access on a weekly or monthly basis, you are still responsible for showing a minimum of five articles per day to Google users. Otherwise, your site will be treated as a subscription site.

You won't get a referrer. Googlebot is not like a real user, surfing from site to site. What Googlebot does is this (more or less)

1. Googlebot requests a standalone page
2. Googlebot parses the page out. During this process it notes the links on that page and, depending on various mechanisms (nofollow, internal page rank, the mood of Matt Cutts, etc) it will note those links for the system to parse later
3. Googlebot is done so it grabs another page off the page list (likely without know how it got on said list) and goes back to #1

Now, to your question. Since Googlebot has no referrer it won't get your alternate content. This means that your alternate content page won't get indexed.

I would suggest here that a best practice is NOT to filter on referrer data, which can be inconsistent and potentially fake. Instead, I would make a separate page that contains your extra data and allow users to decide if they want more information Thus Googlebot finds all your content and your users get a better experience.

Not really. Google is looking for unnatural links and patterns. A single sitewide footer link isn't going to impact SEO that much. If the sites all share the same server/IP Google will likely just devalue them (not penalize) and move on. If you're still uncertain you can always nofollow them.

The only exception would be if you're trying to link targeted words in the anchor (which does look spammy). Just link the site names.

Danny is right. You can't geolocate a site to a continent. Goelocation assumes you're targeting a country or language.

I wouldn't bother with a site.asia domain either if all you're worried about is latency. Instead, what I would do is work on geolocating your site. For instance, Amazon offers geolocation in their Route 53 product (country or latency). So you could host your site in the US and a copy in one of their Asian datacenters. This way, your visitors (and robots) will always go to site.com, but be served the fastest instance of your site. This avoids the duplicate content problem entirely. There are some other services and hosting out there that could probably help you do this as well.

In most cases, no. I would still add language tags to your site, but Google tends to view different language sites as localized to that language.