I know those are the rules, but I have so much fun stamping, that I will stamp the bills then enter them. I'm thinking, "No harm done!" And it's not like I stamp them without entering them. Well, yesterday morning I stamped all my bills then went to enter them. Apparently, every other Georger had the same idea and the site was very slow. I had to go to work and realized...I had some marked bills that weren't entered! So I had about $15 worth of money I couldn't even use. I put it in a different place in my wallet so I wouldn't accidentally spend them and cause Hank to get "stamped, but not entered" messages!
So, a real life example of why you should always follow the rules!