Wow - I am seeing some answers I'm troubled by.
I don't believe that "casual" dating is a good idea. If you know it's not good for long-term, then by definition, you're leading them on; you're either using them as a safety blanket, toy, or crutch, none of which is a very Godly thing to do. It's not to say you can't be friends, but dating and sharing intimacy with someone you have no intention of marrying is pretty much just selfish or irresponsible. SOMEONE always becomes more invested in the relationship, so they get unnecessarily hurt. For what? Fun? Comfort? It just makes no sense.
Regarding dating of a non-believer, it makes no sense Spiritually to become romantically involved with someone who doesn't share your sense of reality. I wrote a long time ago that the Godly purpose for dating is to find a spiritual partner to marry. A spouse needs to be an anchor to reality. If you can't agree on what reality is, then you are tethering yourself to a time bomb. Unless of course your sense of spiritual reality is that God isn't really that big of a deal, and that there are more important things in life than heeding scripture. Whether something is statistically probable or not should have no bearing on whether you persevere if it's the right thing to do. The cards of your future are stacked by a knowing, wise, and loving God. He will use you, willing or not - blessed or not - to stack the deck in other people's lives. If you are unwilling to be submissive, prudent, obedient or responsible, I don't believe you're going to be very blessed in your relationship, and most tragic of all, God will certainly not be glorified in it.