This post over at Coding Horror and this one from Read Write Web seem fairly related and are just more voices to add to what seems to be becoming a torrent against the cloud (maybe that should be wind).
Aspects covered in both of these are some of the reasons I'm migrating my photos away from Flickr, why I stopped posting to my Tumblr blog (and created snippets here instead) and why most of the (rather large amount) of content I produce is now hosted on sites I own. It's also partly why I've stopped using things like Google Docs. It was one of the reasons I didn't move my site(s) to a hosted Wordpress.com account.
That's not to say these services don't have benefits. My photos on Flickr have had far more comments and favourites on them than they will ever get hosted by me. My sites get far fewer visits than if they were part of a network, because they tend to do cross-promotion. During the re-design I shied away from comment services like IntenseDebate (despite the fact that I trust Matt Mullenweg) and Disqus. When this site dropped out of Google's index back in Jan (for no reason, it's been happily listed for five years) my site traffic dropped by about two-thirds, lucky I don't rely on this site for my living, I'd be looking for a way to sue.
Some of these services seem to be moving into the realm of utilities, imagine if one company ran the email system and suddenly went under, it'd cause chaos, well some of the social networks and other sites are starting to become platforms and governments may have to step in and protect some of them in the future to keep the rest of us running smoothly. In the same way broadband is slowly moving from a luxury to a necessity online services may do too.
I haven't got an answer, I hope some of the smarter people out there will, but I like open standards more and more.