This post is not meant to support hacking in any way, just expose what it is exactly for those that don't know.
Some of you may have seen this already. I kind of hope more people do, if it gets embarrassing enough for EA maybe they'll address this problem.
For those of you that don't know BF3 seems to make the client authoritative on certain critical parts of packet data much more so than other games do. This means that its far more vulnerable to hacking than a lot of FPSes are. Usually there is server side authority on data like bullet damage, or other hard values that are easy to check mathematically.