Video chat is an excellent way of verifying the visual identity of someone.
If someone refuses to video chat with you for even a minute, there is a good chance this person may not look like the photograph (or photographs) he or she is using.
Though it seems no networking site is entirely immune, many are now finally taking the matter seriously and implementing more elaborate security measures.
Nevertheless, scammers are becoming more and more sophisticated as well, finding and exploiting any available loophole.
The better sites can block these types of tricks, and are doing so each day with more and more sophistication.