Pretty much everyone who gets marginally good at the game gets called a hacker at one point or another. I remember being banned from The Game Wardens' old server in early 2011 (along with my friend, for no reason) because I was killing people through walls with the magnum. They claimed to have recorded demos that showed me "passing through walls" or something. I actually had to find them on their Ventrilo server and sort things out, which they were at least willing to do instead of plugging their ears and whisking me away.
It's a shame, but with Source's questionable hit detection, client-side blood not representing hits (though the hit sound helps), latency, and the game's general learning curve, hacking accusations do get thrown around a lot more than they should.
