Check out the body image forum
http://www.3fatchicks.com/forum/forumdisplay.php?f=219
and the loose skin faq
http://www.3fatchicks.com/forum/showthread.php?t=36040
There are a number of contributing factors to loose skin including age, highest weight, overall time at high weight and genetics. Some people are blessed with minimal if any loose skin and others are well not so blessed.
Loose skin also firms up some what as time goes on. It really depends on your individual factors though whether or not you'll have loose skin and whether or not it'll firm up.
For me, losing nearly 140 lbs has caused some loose skin but it isn't too bad