This idea of minimizing the caching layer and instead allocating those resources to keep as much of the database in memory as possible is seriously underdone. I know memcached is the trendy thing these days, but some of these memcached layers out there are as big as the database layers and add all the complexity and inefficiency of dealing with cache consistency. Often it would be better to keep as much of the database as possible in memory and maximize the performance of the database (with careful indexing, partitioning, replication, and materialized views).

Seems obvious that the solution to a slow database should be fixing the slow database, but the much more common solution is to put a lot of stuff in front of that slow database that tries to hide the shame.