Recently found out that my husband lied about his faith in Christ before we got married and he is only Christian by name because thats what his family is. Let me tell you, it is very difficult being with someone like that because without Christ in their heart they are vulnerable to the influences of immoral friends and Satan himself.
I think its best to keep unbelievers as friends and stay strong in your faith. Be an example to them and show them Christ's love so that they will except him. On the other hand, I did used to be with an unbeliever for a very long time and he excepted Jesus as his savior while we were together and he still goes to church to this day. We are still friends and talk every few months and its so fun to talk about the Bible with him. Sadly, this is the exception and not the rule, the majority of the time things don't work out like this. Perhaps he still would have become Christian if we had stayed friends and never started dating in the first place.
I know, I'm giving 2 different answers...but for the most part I don't think its wise to date an unbeliever and we should obey God's word by not being unequally yoked. I agree with the above posters that the purpose of dating is to try to find who you want to marry, so why waste time dating someone that you will most likely have to end it with anyway? I say save yourself the headache.