Storing IP addresses?

Hi,

I was just wondering, is it typically for web developers to store the IP addresses of users that do actions on their servers.  For example, if I created a message board, would it be normal or a good idea to store the ip address of each person that makes a post.  I figure that this could be useful in banning ip addresses of people that are putting spam on the server.  Assume that the site does allow anonymous users.
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