I wasn't sure if it's safe or not. It seems there is no problem, my bad.
What is a Steam ID?
When someone signs up for a Steam account, a unique identifier is allocated to that account. This is a Steam ID. A Steam ID is public information and is safe to share with other people. You should treat your Steam ID the same way you would treat a link to your Steam Profile.
And come to think about it.. it's normal, because anyone could look it up anyways. More, if you've linked your steamid to your account on AC forums for example, I can see it directly. D'oh !
All right, now you need to find that magic number (or nick, if you have a custom URL). Here's a simple way:
Once you did find it, please add it in your registration post. I'll setup the entry_list using this information.