I just got a nasty bill today from my hosts. During October our sites traffic fell form 1200 uniques per day to about 700. The funny thing was that my host for the first time ever asked me to pay excess bandwidth charges! I scratched my head checked my stats and yes they were right I had exceeded my quota. I checked everything else page hits = down, uniques = wayyyy down. Everything down but bandwidth more than doubles. I even went to the extent of checking my Logs to see if anyone was hijacking my images etc..nothing!. I haven't changed anything about the site either. Help me someone has anyone had this before?
Hijacking images would be the usaly cause of blame. I think these image theifs are getting pretty smart, it may be worth having another look over your logs to check for things that dont quite add up. Spiders can also be bad for your bandwidth, I would sugest using a robots.txt that excludes as many of the bad guys as possible.