MySQL Field Length

[eluser]insub2[/eluser]
Can anyone explain to me in simple, direct terms why it's not a good idea to make the length of all my fields really big, say 255. I've read that I should only have them as long as they need to be but no one is really giving a good reason. AFAIK, there isn't any space saved. So what is the reason?


...it's easier to just put 255 than to think about how long things will need to be. :-P