> One thing I find fascinating, and have not seen discussed, is what will happen to all this data in, say, a couple hundred years.

My prediction: If Facebook looses popularity like MySpace: it will hold onto dead people's profiles as long as possible, until it finally goes out of business or its skeleton team of developers makes a critical mistake. Their business at that point will basically be like that of domain squatters. They'll even start sharing things hidden from the public behind privacy settings. If Facebook remains popular, however, it will eventually aggressively purge the profiles of the dead to focus resources on more lucrative monetization opportunities of active consumers.