I think that the birth control / pregnancy issue is one that writers just can't win. If you had a show where characters were sleeping around as often as they are on Grey's, and pregnancy and/or STDs were NEVER brought up as an issue, we'd all be saying "Just how realistic is it that these people could have this much casual sex and never face any consequences?" On the flip side, when they write those things in, we sit back and say "Don't they know better?" But I gotta say ... if this was a show where characters didn't sleep around, and didn't face the drama of pregnancy, STDs and other things, I'd be bored with it and probably wouldn't watch. I don't watch Grey's for realism, and I'm glad they don't bore me with it!