Your concern about social networking data being used in ways that were not intended by the owner of the information is a valid one. However, this happens all the time -- our data is sold to publishers, banks, credit card companies, credit reporting agencies and the like. Our junk postal mail is a daily tribute to the fact that our personal information is being bought and sold and is available to just about anyone who wants it.

The advantage that I see with social networking data aggregation is that you can provide only that information you want to have made public -- you can withhold personal information, for example. Plus, if a standard for this type of aggregation was developed, there could be an opt-out provision built into each social networking site. For example, if I posted my data on Facebook, I could check a box that would restrict Facebook from sharing this data with other social networking sites. Plus, we could always change our data, delete certain parts of it, etc.