And since we just discussed this on another thread...
The experiences of others (including me) don't mean that it is an absolute. 99 people may not have their ID or validity checked, and 1 person may. You may end up having the same experience as the 99, or the 1.
Also, rental car companies are really struggling now. They are not just raising rates, they are increasing enforcement. Enforcing the use of discounts is one way to minimize losses. What happened to people in 2008 and 2007 really doesn't mean that it will happen in 2009 - we may well see more stringent enforcement in 2009 due to the dire situation of the rental car companies.