Okay, her is your tip of the week.
As advised, I tested the cleaner I have on my area rug just to see how it would work. It's upholstry cleaner that I had handy so trying it on the rug was a bit of a goof, but boy did it work well. Anyway, what truly got me was as I was trying my test section, a huge amount of dog hair started popping up.
Now I vacuumed pretty well (beater bar and stuff) but this was stuff that was obviously way down in the carpet. The more I brushed the top of the carpet with this can's brush the more hair came up. I was quite shocked (even though I know carpets are filthy things at the best of times). I think I got a little pile of hair as big as an egg from doing maybe a square foot, and that was on a corner not a centre section.
So, if nothing else, I highly recommend the brush on the can (although the cleaner is very good too). Between the fine little bristles and it being plastic and causing like a static type reaction, it really finds the pet hair that is deep down. I didn't even have to rub particularly hard, just several times and then switched directions and whap, a clump of hair would appear. I've tried other rake type versions of rubber brush before but nothing has ever worked like this.
Now if they could find a version that didn't require sitting and doing it foot by foot, that would be great.