Most people, presently and in prior generations, had one face for public consumption and another for private (sometimes more than one for each, depending on the variety of audiences). But the vast amount of information recorded about us through modern technology makes it less and less possible to maintain clear separation of our private and public utterances and activities. Someone who wants to investigate you will be able to find a wide array of sources in moments, and not all of those will jibe with the persona you present on a resume.
I'm inclined to think that decisions are best made with the maximum amount of relevant information, and thus am not overly concerned about this development. If you have grandiose ambitions, your employers might want to know that you view them merely as a stepping stone. Discussion of someone's character might be good for future lovers or professional associates to know. And I think it's always useful to know if someone is a two-faced liar who advocates one thing among Circle A and another in Circle B. The more of your life is online, the more likely it is that others will be able to access this important data.
Some information is, of course, not relevant for making certain decisions; the size of one's breasts, for example, is not important to whether or not someone will be a good attorney, and thus only idiots would be motivated to make employment decisions based on online discussion of such things. But the more accustomed people get to sifting through this array of information, the more experienced they will become at culling the useless from the useful. Anonymous attacks could be discounted, but they might also be an indicator that people feared to criticize openly for good reason. Decisions about love, work, and play can be made holistically, with less fear of surprises.
And the more formerly-private information becomes available and openly discussed, the more norms will shift. In the last hundred years, we have embraced the privacy norms of an industrial, urban society in which people know little about others, aside from the content of their carefully constructed public personae. The collapse of one's ability to self-define a persona and manipulate other people's perceptions will thrust us back into a more natural social dynamic, in which we are aware of the reality behind the masks and can make our decisions about morality, social standards, and interpersonal relations on a more accurate idea of baseline behaviors. Viva MySpace.