It's true. vBulletin's search function is not one I've ever really liked, and it's based upon a backend db search system which really requires quite a bit of tweaking to get just right, and even so it usually forces the site admin into making some unfortunate tradeoffs to keep it working acceptably well on high-traffic sites. This isn't helped by the MySQL documentation much either. It's not bad documentation but it's not great.Search features on forums are VERY heavy on resources, so they are usually set pretty poorly to minimise the resources they use.
Y'know, that could be read the wrong way. . .Just wanted to clarify, the site search requires 4 letter words at least..