I've noticed a sort of similar effect with old-fashioned adventure games (the kind that LucasArts and Sierra used to make). The existence of the Internet and GameFAQs has effectively ruined that genre for me. Part of the fun was spending hours on end frustrated when you couldn't solve a certain puzzle, only to finally come up with the solution and get a major feeling of accomplishment. These days it's far too easy to search the web for a solution whenever one starts feeling in the least bit frustrated. (And then when you have the walkthrough open, look up the solutions for the rest of the puzzles as well...)

I've also noticed that if I'm solving math problems and a complete model solution exists, I'm far more likely to give up early and look up the right way of doing it. If there were no such solution available, I might work on it far longer and eventually solve it myself.

A somewhat promising approach I've been experimenting on is to tell myself that no matter what, I need to work on this set of math problems for at least (say) an hour. That reduces the incentive to cheat, since I know that it won't save me any time. The hard part is in actually sticking to this.