I often wonder with stats like this (and of course there is always the old adage - There's Lies, Damn Lies and then Statistics) if it's not really an increase in bites, but more of an increase in reporting them.
Also, what constitues a "bite" - My dog bit me - but it should not go towards these stats as what actually happened was I managed to put my hand in her mouth when she was barking - don't ask, I still can't figure out how I did it
. She didn't break the skin, but did break a bone. Of all dogs I have owned or have known, she is the most unlikely dog to bite deliberately, so had I've told the hospital what happened, this would have been recorded in the above stats.
The other thing is that hospitals are now recording and reporting this information, whereas they didn't used to.
It may also be due to an increase in dog ownership, for example there are thousands more car accidents than there were a hundred years ago, so cars must be becoming more dangerous right? 
So, I feel that this is just an inflammatory piece of meaningless journalism, as someone else said on another thread "Family buys Staffie and it becomes a wonderful family member" just doesn't sell as many newspapers