== More code always means more potential loopholes == 

 "Ajax opens up another attack vector for malicious code that web developers might not fully test for." 

 While technically true, I am not sure that it appropriately conveys information. It gives the impression that Ajax is somehow specifically insecure which is not really true. (please note that I said "gives the impression that" and not "says that") It's just that more code and more communication means more opportunities for bug and security vulnerability. I am going to modify this. Let me know if you feel my contribution is inappropriate.