The one thing to keep in mind with 37signals advice: I assume they are building-out and maintaining their own boxes (TaDa List being the one known exception). C

The one thing to keep in mind with 37signals advice: I assume they are building-out and maintaining their own boxes (TaDa List being the one known exception). Could be wrong about this, of course, but not all startups have the luxury to do that. If one can't afford to rent or build-out boxes stuffed with lots of ram goodness and super-efficient raid setups (perhaps 37signals has a dedicated highly optimized RAID-10 file server? that would also play into their ability to run from a single server), then sharding becomes much more important much earlier in the growth curve. I've always viewed sharding as a poor-man's approach to scaling (with the exception being rich-man's boundary condition sites such as flickr and facebook that have absolutely no choice). And, of course, let's not forget that memcached can play an important role for most people. The number of read queries they're executing might be 90% fewer if they're utilizing memcached properly.