I work for a company that averages around 50 production deployments per day for our customer-facing ERP, and we only do code reviews for new devs and changes to underlying framework changes for mostly the same reason sklivvz1971 mentions. We rollback very infrequently and a majority of our devs can deploy to prod with the push of a button as needed (this includes both application and database code). Not arguing that code review is unnecessary, just feel that with proper training and having devs with good judgement can help reduce the likely hood of breaking things when deploying small changes frequently.