They probably stopped raising your limit because of the credit crisis and new regulations. If you are planning a large purchase then call them and ask for a higher limit. Although with current rates you might be better off finding financing through the retailer or getting a new card with promotions. If you have a good credit score you shouldn't have a problem either way.

I don't think raising a limit "just because" makes a lot of sense. Some say it effects your credit score in the long run, but chances are they'll pull your credit when you ask for a raise and that will just lower the score.

What should my credit limit be?
In the film The Social Network Mark breaks up with Erica Albright early on, this (through a series of steps) leads to him creating The Facebook.

However in real life Mark is married to Priscilla Chan who he met at Jewish fraternity at Harvard University in 2003 (Facebook was founded in 2004).

Does Erica Albright exist? If not why is she featured in the film and not Priscilla Chan?
