Laws concerning info from opt-in forms

[Rankenstein]

Hi guys,

First off, I'm going to be looking into this myself but I would appreciate it if someone has a potted summary (or could point me to a good thread about this).

There's a couple of forms that surfers can fill in on my site, one is for people who sign up for a newsletter, the other is for enquiries. I've got no intention of using their info for any nefarious purposes, but do I have any legal obligation to destroy it, or keep it in a high-security bank vault, or something?

Is this something I need to worry about, in other words?