Day 4 - Data Security

As I am a member of social networks and a customer to various companies as well, I tried to think of any reservations that I would have about this. And the first thing that came to my mind is obviously data security?
How can I as a user or customer control who is using my data for what? We all know how many spam we get every day, but this is sent more or less blindly to a large number of recipients.
When companies have more data about me, will this lead to even more unwanted email or will this filter the advertising and reduce the amount of communications while increasing the quality?

I think this could be a tightrope walk for companies that think about implementing CRM 2.0. A strict governance needs to be put into place that ensures that the customer data is not abused in any way. Any affairs in this area could seriously harm a company or its affected brand.