I'm okay with factory overclocked cards in reviews, so long as the same benchmarks are ran on all applicable cards in the write up. Both stock and OC'd cards are available for consumers to buy, so information about the performance of both is required for a consumer to make an informed purchase decision.
Now, aftermarket OCing of the video card can get sticky. In my opinion, its okay, so long as the OC'd cards are both shown as stock speeds as well. If you benchmark a stock card against an aftermarket OC'd card, thats not really a fair competition. Not everyone overclocks, and for many, that aspect isn't something they care about in the slightest.