That's a tricky one!
As a parent, I'm quite liberal.
However, I don't want my kids being exposed to drug abuse and violence as well as swearing. (I hate seeing kids swear - I've heard plenty a kid use the "C" word. The four letter one. Ending with T!
) - simply because their parents say it. It means nothing to them, but they still may copy it.
Since my kids are currently young, I don't think it really matters as much, but when it's older, I will be more careful what I'm watching. For example, no Jerry Springer (*grins*) will be on in our house (I don't watch it really!!). At the moment, I cover my eldest kid's (2 years) eyes at certain things - too violent scenes, and drug abuse.
Currently, for example, I'm playing Metal Gear Solid 4, and the main character keeps sticking these injections in his neck - I cover my eldest kid's eyes then.
I think one should be sensible. Children copy what they see, and when they are too young to understand it's only imaginary, it can be harmful. My nephew used to kick and punch other kids because his parents never censored what was on, so I wouldn't like to make that mistake - but I don't want to be the kind of parent to screen EVERYTHING!
Gah. I'm stressing out now.