a query on a statement on statsFollow

Taken directly from Aldriana's FAQ:

Q: What's this crit cap thing you keep talking about?
A: Due to the mechanics of the hit table, there is a theoretical maximum of how much crit you can benefit from on white attacks. In particular, if your chance to crit, chance to miss, and chance to be dodged add up to more than 76%, you are crit capped and thus not making full use of the crit on your gear.

As an illustrative example: let's say our miss rate is 10%, and we are expertise capped. If our crit rate is over 76-10=66%, we are crit capped. So if our tooltip crit with full raid buffs is, say, 65%, we're okay... unless there's a crit debuff on the mob (Master Poisoner, etc.). If we have this crit debuff, our true crit rate is then 68%, meaning we are "wasting" 68-66=2% crit on white attacks.

It is most common to have problems with this during agility or crit procs (Dark Matter, Death's Verdict/Choice, etc.) but by late ICC it is quite possible to be passively crit capped. If you're crit capped - either through procs or passively - you will often (though not always) find it advantageous to socket expertise (up to the cap) and hit so as to raise the cap to the point where you are no longer wasting crit.