I still think Web 2.0 is missing some kind of app aggregator. Something that would both improve the findability of applications, and allow them to be plugged together similar to what yahoo pipes does with RSS. However, without some kind of standardization amongst the apps, this is way too complex to implement.

And creating a trusted distributed computing system on facebook, where clients would compete to have users give their programs highest priority. On a simple analysis, while this would not be a very dependable system, it seems cheaper than Amazon's service at $1 an hour per core. Plus, this could be made more complex by integrating a contract system - clients can promise a certain payout based on the results of their program, kind of like the lottery.