Are you suggesting that #frenchlaundry.wine and #wine.frenchlaundry be synonymous, or that the order be hierarchically significant? How do current hashtag parsers and search engines deal with such tags?

I believe they'd need to be hierarchical otherwise you'd just do two hashtags for the same effect.
#wine #frenchlaundry --VS-- #wine.frenchlaundry

Andy - I think there is a straightforward difference between #kathysierra.w2e and #w2e.kathysierra, for example. The first term could be the primary location on a website, and the second a subsidiary page. Depending on your perspective, you might be subscribing to RSS feeds from #kathysierra, and yod'd also get stuff related to her preso at the Web 2.0 Expo. And in the alternative, vice versa. The issue can be considered 'hierarchy' but might be better considered as which term is primary.

Cody - As I comment in the post above, two hashtags are not the same as subtags, in their semantics.

Question: I wonder if this idea would be an extension of subtags or a separate proposal.

Problem statement: Event hashtags of course point to a search of other tagged tweets, but quite often I want to know (1) the full name of the conference and (2) the link to the official site. It would be extremely helpful to have a syntax such as: #event09.web http://url.ly so that you know right away that the link following the tag is to the official site.

The success of this strategy depends on a few helpful souls using this syntax, a kindness of strangers mechanism.

Another approach is possibly worthy of a proposal, but it could be well beyond the scope of microsyntax --- how about an "event tag register" that would somehow be queried and kick out an URL upon initiating a hashtag search of a registered event, many details yet to be thought through.

@Howard Liptzin: I don't think that makes sense. It would add a LOT of redundant information to conference tweets as everyone only needs that information once.
So I don't think it should be microsyntax. A database for conference hashtags (that may be queried by clients) makes much more sense.

tagal.us (http://tagal.us) already provides a register for hashtags, which can be queried
by Twitter clients using specific syntax (hashtags can be defined the same way).

A separate register for event/conference hashtags means that there should be a way
to differentiate a hashtag, which by nature can be used for a wide range of topics, from an event hashtag.

I don't think there's a need for an event-specific syntax.
What's clear is that non-intuitive hashtags (those that are mostly used for scheduled events)
should be defined prior to their use (but that goes beyond the scope of microsyntax).

thanks for the feedback.

@CWagner: I didn't mean to suggest that this syntax should be used each time the hashtag is invoked. As you correctly point out it's a huge waste of characters and too cumbersome. I just thought that it would probably be used by a few people at the beginning of an event and a search of #hashtag.web would yield a quick pointer. It seems like the event use case is *very* common and is bound to remain so, it seems to me like a solution assisted by microsyntax (even if it has nothing in common with mine!) would be welcome by a large number of people.

@vincentlgvl: great tip on tagal.us. I still maintain that since the use case is common, a solution that envisions a microsyntax hook might be worthwhile contemplating.

Having said all that, you are right, it's probably most elegantly solved on the client side with supporting services such as tagal.us or a semantic search engine, blah blah.

Would it not be better to use a slash? #GreysAnatomy/SeasonFour as opposed to #GreysAnatomy.SeasonFour?

And, won't these show up as two different items to twitter anyway? They stop the link after punctuation, right? It's like putting a space in there.