I think it's common courtesy for the date asker to pay. To use a personal example, my ex asked me if I wanted to go out to lunch one afternoon. I met her at a restaurant that she chose and she got what she wanted and dessert, then expected me to pay. She had to leave for work right after that. To me, it seemed like she just wanted a free lunch before going to work, not to go out on a date. If you're a girl, don't ask a guy out just to get him to pay, that's crappy. At LEAST go halfsies in that case.
Also: Page 5
Also: Page 5