If you ignore the fact that the events aren't mutually exclusive, the odds of at least one person being dealt any pocket pair are:
1 - (16/17)^10 = 45.4%
Given that one person is dealt a pocket pair, the odds of at least one more person at the table being dealt a pocket pair is approximately:
1 - (15.78/16.78)^9 = 42.5%
That puts the probability of two or more people having a pocket pair at about 20%, or about once every five deals.
There are some things I've ignored in the calculation, so it's just a ballpark number. It does show that it happens more often than you might think.
As far as the KK vs. AA example, that should happen roughly once every 500 hands. Thing is, you'll probably see the hole cards almost every single time it happens since no one lays them down preflop, and an A will appear fairly infrequently to scare the KK.