About 4 times a year. Usually it’s because someone says “who wants lunch” and goes and picks up fast food. I don’t really go out for fast food myself.
Umm… about 3-4 times a week. Usually. I can’t cook in the dorms, and the cafeteria has limited hours.
When I’m more cash-strapped, (is that possible?), it cuts down to just once, if that.
2-3x a week.
Almost everyday, which is pretty nasty, now that I think about it… 
If you count Taco Cabana (a TexMex fast food chain that uses fresh ingredients), maybe once every week or two. If you just mean the big fast food places like McDonalds, maye three times a year (mostly on road trips).
Twice a year I get Egg McMuffins or a Happy Meal. I never eat it at home, just when I’m on a road trip to my mom’s.
Maybe once a week.
If you count pizza, once or twice a month. Otherwise, essentially never. I’ll get a sandwich at Subway maybe a couple of times a year, and I can’t even remember the last time I set foot in McDonalds et al.
Usually 2-4 times a week depending on how broke I am and If I am at school or on break. Since I commute 20 miles to school and don’t live in the dorms, I’m forced to eat out a couple times a week since I don’t have time to drive back home during my lunch break and I don’t have meal tickets to eat at the cafeteria.
About six times a year.
Once every four to six weeks.
About twice a month, and only from independent or small outfits. No major chains.
Crap. Make that once a month. When I’m pre-menstrual, McDonald’s french fries are like little soggy pieces of heaven to me.
Four or five times, in the last decade. I think the last time I had a McDonalds was seven or eight years ago.
2-3 times a week.
Probably two or three times a month. Mostly from a locally owned burger joint that has the cheapest food ever. My husband and I can both order and sandwich and fries, and he can order an extra side and it only costs us about $6 total to eat there. I go to Subway every once in a while, too.
3 or 4 times a year. Only when I’m on road trips.
Although last summer, one night we were debating what to have for supper and we decided “let’s go get some whoppers and fries”. I think that’s the only time we’ve done that in 7 years.
Reading the responses, I think I have a different definition of fast food than other people do.
To me, it means McDonald’s, Burger King, Wendy’s, Taco Bell - places like that. I guess KFC too. Not pizza. Not Mexican food from a takeout place if the food is made to order, unlike Taco Bell. Not cheeseburgers from a diner, or $12.00 cheeseburgers from the French restaurant down the street.
Based on my definition, I eat it fast food maybe once or twice every 18 months.
Once a week I indulge in Steak and Shake. It’s my dirty little secret.
Once in the last 2 years. Before that it was about 4-5 times a week.