Maybe they feel safe on the net

Simple, you have not met them in real only in screen. In screen all people are just image until you really meet them someday in real then you will know. You can flirt someone in virtual then suddenly disappear. It is virtual life. You can be somebody else in your own world that you create it there.

I have noticed this very thing for a long time now. I lived in Taiwan for some time and many people acted this way also. It is a cultural thing, as well as the freedom to do whatever you want online. From what I learned about traditional Chinese culture, it is not really decent to show affection or to flirt in public too much, especially with a 外國人. :-) Many people are too embarrassed to even hold hands. Every coin has two sides. Yes, Chinese culture is complex when it comes to this issue. Westerners tend to be more straight-forward and to the point.