What Psion and Thirdwizard said: I expect house rules to be reasonable, and I expect them to be acknowledged before the game starts. In my personal opinion, a good practice is a Word document (or text document, or RTF, or whatever) with all of the house rules in a game. If it's not in the document, then it's not in the game. House rules can be added, but I prefer if the whole gaming group talks about it, first. House rules can make or break a game.
As regarding the original post, there are house rules in all sorts of games. Where does the original poster think the term "house rules" came from? It's not a term that derived from roleplaying games. Often, the rules deviate and another game is formed. Texas Hold 'Em is different from 5-card stud.
I love house rules. I love different variations and flavors of games. I love homebrewed campaigns and different worlds. But I prefer those rules be designed by someone who understands the game. A few examples of the opposite case have already been cited.