Use rel=canonical to save otherwise squandered link juice?

[cadenzajon]

Oftentimes my site has content which I'm not really interested in having included in search engine results. Examples might be a "view cart" or "checkout" page, or old products in the catalog that are no longer available in our system.

In the past, I'd blocked those pages from being indexed by using robots.txt or nofollowed links. However, it seems like there is potential link juice that's being lost by removing these from search engine indexes.

What if, instead of keeping these pages out of the index completely, I use to reference the home page (http://www.mydomain.com) of the business? That way, even if the pages I don't care about accumulate a few links around the Internet, I'll be capturing the link juice behind the scenes without impacting the customer experience as they browse our site.

Is there any downside of doing this, or am I missing any potential reasons why this wouldn't work as expected?

[RuthBurrReedy]

I'd recommend not using the canonical tag here for the following reasons:

• It's not what the tag is designed for.  By using canonical tag you're saying to search engines, "this page is the same as this other page so just ignore it."  Not true in this case.
• It seems like the pages you're noindexing are good candidates for it: they aren't pages that would be a good experience for users to land on from a search.

IFor product pages that are no longer available, I'd use a 301 redirect to point users to the home page or a similar product - that's a way better experience for users who click on links to those pages (remember, it's about the users as much as search engines), and you preserve link juice.  I'd also just double-check and see if your "view cart" and similar pages are accruing many links; my guess is they aren't.  I'd keep those noindexed via robots.txt just because it would be very odd for a user to click on a search result and land there.  A good user experience is more important than the (my guess is very small) amount of link juice you might lose by not having them indexed.