Some web sites and services make it less than trivial to close your account if you should need or want to. You would think there would simply be a "cancel my account" button somewhere - and sometimes there is, but not always by any means.
To that end, here are a couple of websites that list the ways to extricate yourself from service XYZ should the time come. Both of them give you an idea of how difficult it may be to delete an account from a particular site, along with details on the process.
Both seem to be pretty current, after I did a random check of several sites from each.