With the demise of GPU mining also came the demsie of mid size mining pools. 70% of the hashrate generated today is in ghash, eligius or btcguild.
As the hash rate has increased and a pool for whatever reason does not gain enough to stay even with growth, everything is fine until unlucky streak sets in. The pool then loses users and a snowball effect happens. Mid size pools to me are one of the most important features, they absorb users when a bigger pool fails (we have seen this happen many times now) and keep a basic balance in check.
Remember, everything is fine until the second it is not.