Certainly not! If I was re-selling the data, maybe. But I'm generally using it for statistics and data viz. I include the source of the data and I always obey robots.txt. Sometimes I'm even able to talk with the owners beforehand to get their ok.
In an earlier age, I ran everything through squid to consolidate browser caches. About five minutes after setting it up, I realised that pulling all the references in the log file and then indexing the lot with htdig would be tremendously useful when I was on the road without internet access.
I spent way too much time pruning stupid crap such as slashdot and started to learn this 'Bayesian classifier' thing.
(Don't downvote him, it's a valid question)