Was playing in smp today and was throw out of the server with a "hax off plz" notice.
At first I thought it to be a bug in the server software at hex 0F. Apparently it really meant "Turn off your hack please." and that you shouldn't be using any modification or a modified client.
That was my first warning received. The problem is, I don't use modified clients nor do hacks, and have had requested on IRC to look in to this issue. Thinking that there may well be a bug found here, and wondered how many players may have had been wrongly banned by this. Lets us suppose I'd to just write-off the notice thinking oh well, back to the game. Then the same thing to happen to me again, and then again later on then "Ban"!
It turns out to be me moving my mouse too fast while doing things in my inventory that triggered the above event. True, I was very quickly making wooden planks at the time. On my return, the wood in my inventory was gone but the three wooden planks were still there.
This brings me back to wondering about the possibility of some players maybe wrongly banned. That is why I felt it to be important to have this brought to the attention of the server administrator.