pixel_juice - 5:25 pm on May 15, 2003 (gmt 0)

>>they delivered more traffic than Google, MSN and AOL combined

How much traffic you get from Google etc. depends entirly on how well you are listed. Are we talking big numbers from good listings? If we are then this is highly suspicious.

Although, as Chris says, you seem to have a fair bit of evidence, if I were you I would be looking extremely carefully at what the visitors sent by your competitor do. What are the IP addresses? Do they click through the site like normal visitors, and most importantly, do they convert? This is the crucial question rather than whether the numbers add up, and should tell you if they are up to no good.