A short list of things that sound like a better idea in theory than they are in practice:
Bagel sandwiches
Airline food
Angry/Spiteful e-mails/blog posts/comments
Classes taught by famous professors
Most movies by Sam Raimi
Most video games by Troika Games
Most books that you read because it's a book that you should read rather than a book that you want to read
Any other suggestions for the list?
Grilled Cheese made with cheese fancier than Kraft singles