Personally, I don't think people are all that different online than they are in person. You can find a cheating guy in church... I would know, I dated one. See, people are people, human nature is what it is. You will find all kinds of icky people in church, people who abuse the grace of God or aren't saved at all.
Now, the internet does allow for some advantages, I'll give you that. You can hide kids, baby mamas, drug problems, spouses... all of those things are true. However, you can hide that in person as well. It all depends on what you're willing to see and what you're willing to admit to yourself.
The last guy I was with was for 3 years, and he was a good liar. Very good. He cheated on me, knew scripture, and we went to church together. He was going to be a pastor! Thankfully we broke up, but everyone at church was convinced he was a great guy. It took me awhile to wise up because I believed the line, "Oh baby, I'm sorry, I'll change." Truly, you can be deceived in person or online.