Do you have a robots.txt file blocking your redundant URLs?
I uploaded a new robots.txt file a little over a month ago, I had 308,000 pages indexed (according to site. Today, I still have 308,000 pages indexed, but now Webmaster Central shows over 450,000 URLs blocked by robots.txt.
Mostly different thread modes, and the like.
__________________ ● Please login or register to view this content. Registration is FREE
Most users ever online was 420, that's for my forum and it was mostly bots. It was insane. I think it's normal.
Ya you are right, it is normal and it happens many times so there's nothing to bother about. Actually it could be a good thing that multiple bots are there to crawl the site helping to index new pages faster.