I don’t know if this happens also for you, but for me, every time
a new site asks me to register, I start having problems. Ok it is
free, but you have to give a username and a password. This must be remembered. You should check that it doesn’t leak, etc,etc.
So I will register only if I consider the services that I get absolutely deserve it. After that, you start using the site and interacting with it. Perhaps you discover some problems : for example after having used flickr for some time loading private photos, an error in the server leaked the miniatures of some of these photos in Yahoo image search. And you want to know how to go away and to have every step of yours erased. And horror you discover that this is not possible. Perhaps it is better to know before how is the situation.
For this reason this site (no registration required (-: ) is invaluable.
It connect you with the relevant link and explains to you how this is
difficult and why.