No problem. It just means a thread with a lot of people in it. I think usually anything over four is considered a thread of doom. Mainly because, depending on time zones and RL and stuff like that, it can take forever for threads like that to get anywhere, and it can be tough to coordinate them. Plus you run into the problem of people doing/saying a lot of things in any given post, and then you have to reply to so many things at once... yeah, it's headache-inducing.