Ever since Google launched their AdSense contextual ad program, publishers had a theory that Google had a cap on how much publishers can make. Some believe the cap is a certain dollar amount, some believe it is an equation based on percentages and some don't believe in this cap, at all.
A WebmasterWorld thread has recent discussion around the AdSense Glass Earnings Ceiling theory. If you read the thread, some swear by Google instituting a cap of some kind, while others said they never experiences such a cap. The seniority of members who believe in the cap are mixed also, so who really knows?
Let's poll our audience, do you believe in the cap?
Forum discussion at WebmasterWorld.