Why Twitter is doomed to failure, or what Facebook has to do to kill Twitter

So, added to my list of things that I believe are doomed to failure is Twitter.  Why?  It seems that all Twitter amounts to is a very limited featureset that is easily superceded by the featureset of other social-networking sites.  As far as I'm concerned, Twitter is essentially Facebook status updates with minor additional features.  And I'm guessing those additional features will be coming to Facebook soon, in a much more complete/all-encompassing fashion to boot.  Sooner still if Facebook wants to curb Twitter's growth.  Here's what Facebook needs to do to match Twitter:

• Subscribing to Non-Friend Content: Provide the ability to "subscribe to"/follow people's status updates without being their friends.  People can elect to make their status updates "public" or "subscribable" to their non-friends in order to make this happen.  This is already possible with public videos and public notes, so this isn't much of a stretch.
• Commenting on Non-Friend Content: Provide the ability for people to comment on public status updates.  Again, already possible with videos and notes, so not difficult.
• More Control on Updates: Provide the ability to more finely control what friend updates one receives, and how one receives them, in particular with regard to cellphone integration.  I don't use Facebook Mobile (mainly due to the absolutely ridiculously exorbitant data rates up here in Canada) so I'm not sure how much control one has, but I would assume one does not have the option to receive a text message (or equivalent) for every friends' status update, currently.

Now, here's the additional features Facebook needs to kill Twitter, and other websites, entirely, or at least to aggressively compete against them:

• Generic Publishing: Provide the ability for people to mark any content as public and "subscribable".  For example, a film-maker could make their status updates, notes, and videos public and "subscribable", thus competing with, respectively, Twitter, Blogger, and YouTube.
• Generic Subscribing: Within Facebook, one only gets notifications on updates for items that one has been explicitly marked as participating in- this could be via a tag, a comment, and so forth.  This shouldn't be necessary, however.  If someone posts a really neat photo that I know will inspire a lot of comments (and I want to read the comments), I should have the option to subscribe to said photo whenever updates are posted to it, and thus opt-in to receive comments, etc on it.
• Content Labeling: Provide the ability for people to mark their content with GMail-esque labels, and then set privacy settings, such as subscribability, on that.  This is slightly different from friend lists but perhaps the two could be merged.
• Facebook Connect 2-Way Communication: Facebook Connect allows external websites to report a user's activities as Facebook newsfeed items.  In order to become more seamless, the reverse should occur as well.  Actions on Facebook should also be reflected on external sites.  Currently, for example, one can import blog entries into Facebook as notes.  When users within Facebook comment on the imported notes, those comments are not exported back to the source blog- but they could be, keeping one conversation thread across multiple reading interfaces.  Taking this a step further, why not have my Facebook-uploaded videos also appear on YouTube?

Now, to be fair, I don't actually have a Twitter account, so I may be missing out on some key features here, or mis-representing the featureset.  Still, I can't imagine that there is all that much more that would be hard to reproduce on the Facebook side.

Some of these features could perhaps be introduced via Facebook Pages, so that people could maintain a private account and a public persona as two separate entities, but I think the bulk of these features would be desired by general Facebook account holders.

So anyway, that's it!  Twitter, your time is up.