This is very very true, very often when it comes to more than a gigabyte of data or more then a hundred of queries a second. Quite a few inexperienced devs suddenly think it's big data they've been reading about and FINALLY they can play with it!

With all the hype around 'big data' and all that crap, many people seem to forget how far you can go with plain simple SQL when it's properly configured, and not talking about some complicated optimizations, just solid fundamentals. And no problem if you can't do it, things like Amazon RDS will help you.