An article in the NY Times about people leaving Facebook makes some good points -- Facebook owns all the content, your interests and social networks are mined for commercial purposes, it can cheapen social connections, etc. All are good points, but it's so useful that the problems aren't enough to make me abandon it yet.
It reminded me, however, how lucky we are that the internet itself was created as a government project, with radically open rules. Some sort of wide-ranging computer network was inevitable, but imagine if it had been created by a company, for profit. If we all logged on to AOL (version 15.2) today to do all the things we now do on the internet, it would be much crappier for having years of only certain companies who paid AOL offering content, and no wild and wooly experimentation. And there would no doubt be constant controversies over privacy and use of personal information, except the company providing the network (and maybe a couple rivals, like Compuserve version 23.8) would be the only way to tap into these essential services, so there'd be little consumer leverage. Facebook could potentially parlay its position as the premier social network into something genuinely worrisome, but thank goodness the network itself is, in some important ways, a public space.