Most stereotypes exists for a reason though. I've had the pleasure of knowing people in the field of anthropology, who have shed light on the origin of everyday stereotypes. And I must admit, some of them are extremely fascinating. The most common reasons for stereotypes is either a lack of understanding of another culture's traditions (or sometimes Ethnocentrism) or a fear/distrust of people who are perceived to be "different" from oneself. As Russell Peters says "I don't make the stereotypes, I just see them". The media (knowingly or unknowingly) does its bit to ensure that stereotypes are known to a wider audience. Propaganda spread by the government and media during WWII has led to Germans being stereotyped as Nazis to this day. Whatever may be the reason, at the end of the day, we have innumerable sterotypes floating all around.
So everytime you see a Saudi sheikh, you wonder which terrorist organisation he's part of, everytime you see an Italian, you stereotype him as a Pizza lover (or worse, a Pizza maker! :P), everytime you see a Chinese guy, you wonder how many research papers he's authored, and everytime you see a black guy, well, you feel a bit of a complex. :P
Personally, I'm a fan of stereotypes, just because I love breaking them. Yes, I'm from Goa, but I don't drink (seriously!). I look like I'm a full-on doper (especially in my current state of uncut hair + shabby beard + lack of sleep et al), but needless to say, I don't do drugs (Except caffeine!). I'm from South India, but leave aside the filter kaapi addiction, and you'd be hard pressed to find anything South Indian about me! I may wear more geeky tees than you can count, but I don't remember the last time I spent a day JUST coding.
I also respect people more when they break the stereotypes that form around them on first impressions. Some of my best friends started off as weird stereotypes (kanjoos gujju bhai, flirt delhi gal, 'muh-tod' haryanvi, booksmart nerd girl, maniac biker etc.), and only when I got to know them better did I realise they're the exact opposite of the stereotype everyone sees them as (except flirt delhi gal... you know who you are! :P).
Stereotypes are pretty neat as long as they don't degenerate into racism. When that happens, then we have start having problems, and stereotypes begin to generate divides between groups of people. So it's important to know where to draw the line. But as long as you stay within limits, and are open to having your initial stereotype shattered, I don't really mind stereotyping (or being stereotyped)!
So yes, stereotypes are like rules.... everyone implicitly follows them, but people who break them are always more fun! ;)
PS. Have big plans for the next 20 odd days. Going to be meeting lots of amazing people in the process of doing something I've looked forward to for a long time. This post dedicated to their awesomeness! :)