deb, I'm sorry for the possible confusion, it's possible I was rather terse (it definitely takes some background to get the pith), but that's because I'm already rather sick of repeating the obvious trivia.
so, the short answer to your question: "whether your customers will benefit from the SEO advantages of using .com global tags", is NO, they won't, just because there ain't such advantages for them, in particular, indeed.
there are persistent tales here, supported by the unsubstantiated, generalized statements only, about alleged SEO advantages, but they are nothing but yet another made up myth, being spun out by the automattic Kool-Aid, targeted at the clueless masses, who are mostly ignorant technically and SEO -wise, but all are big into hit-whoring instead.
and yes, the global tag system (aka link-farm) here drives traffic to the .com tag pages, however this does not provide any alleged "google-juice" to the individual .com blogs proper.
real google-juice is all about PageRank. as I repeatedly said here, and no one has refuted it yet, GT, don't affect it in the least way. and if you want your PR get boosted, then I'm all agree with Andy (one of the .com devs):
Come on, post something worth linking to and you'll earn a PageRank.
Call me a purist but I don't care for SEO tricks.
> People searching on Google for "swn festival cardiff" get SERPs that return not only links to sites that mention swn festival cardiff, but also WordPress tag lists for swn festival cardiff.
yep, those SERP rather return links to .com's global tags, instead of links to the relevant .com blogs posts itself.
still can't get it, where's the advantage said for you exactly (but honestly)?
and no, I don't have anything against 'someone called Matt' (btw, a big expert in some really hot ñato special SEO practises), he's just yet to answer several simple questions:
- why can't I opt-out from the GT?
- what's wrong with a compromise implementation a la Flickr?
- why so called Mature .com blogs (which don't benefit from GT at all) are forced to link into it?
and yes, you can also set up your own multi-blog WP version (for whatever strange reasons called as "multi-user") hosting it on your own, but, obviously, you won't be able to make your own global tag pages yourself, because this proprietary closed-source feature is not included in the core distribution. that's why I said you'll need to hire a pro. also, because such linking practises are effectively nothing but link-farms, that are spamming SE indexes, they may get punished -- that's why I also suggested to warrant it beforehand. and that's all about it.
“Use robots.txt to prevent crawling of search results pages or other auto-generated pages that don’t add much value for users coming from search engines.”
don't beleive me? then just ask another Matt (yet he's a friend of the former one ;-), comments are still opened.
so the bottom line is, if you want your customers to bring additional traffic to the Automattic's tag pages, then, yes, stick with .com;
but if you want to provide your customers with advantages like blogs with sane navigation and usability, blogs that don't involved into/rely on SEO gaming etc, i.e. all what .com users are deprived from, then you need something else.
"Reckoners without their host must reckon twice."