obtaining ip addresses

If you already have this guys IP then how come you can’t get it again? If this guy is on dial up(doesn’t have a static IP) then his IP will never be the same. And also if someone has a static IP they can change it fairly easily from what i’ve heard, but the IP’s would be fairly similar. This doesn’t really make sense to me, even if you confirm that it’s the same guy, what good will that do. If this guy is wreaking “havoc” on you and your friends you should be screen shoting everything he does, and logging it. Not only could you report it to Yahoo! but you could also report him to his ISP if you have his ip, you could also turn him in if you had his main email, e.g. email@aol.com email@southwestbell.net if it’s thru his ISP.
I know how to get people’s IP’s but the people on this forum are very suspicious of anyone trying to find someone elses IP. I personally think that IP’s for the most part are useless, unless you are wanting to find out were someone lives, other people will always assume you are up to no good if you are trying to find someone’s IP. Maybe if you had some evidence of this harrassment I’m sure the knowledgeable people on this forum would help you out to get this heckler.
Also theres other ways of finding out if someone is on a different id, checking their IP is by far the best way though, I have had to do this with friends of mine who were playing jokes on me, to catch them in the middle of it. If you get to know someone you can pick up on things, like how they type, an if this guy is a bad person who should be really easy to spot. I’m sure theres many different ways you could trick this guy into revealing who he is other then stealing his IP. I wanna know how you got his IP b4, but can’t get it now, this should be interesting.