I wished everyone understood this. I can't count the amount of times I've heard arguments like "well, we should store this other bit of data in this table too,

I wished everyone understood this. I can't count the amount of times I've heard arguments like "well, we should store this other bit of data in this table too, so we don't need to perform a join to retrieve it". If you need speed, just use a cache (and proper caching discipline) at the highest level that makes sense, instead of micro-optimizing DB access. It's stupid.