We agree with bobbiwoz.
Parks are busy. We were told it was due to southern schools (especially Florida) getting out earlier than northern schools. By Memorial Day all Florida Schools are supposed to be out and they seem to all want to go to Disney.
That is what I've read as well...I'm just hoping it's less than JULY crowds!!
Also that weekend or the previous week is alternative lifestyle week at Disney and you get a good deal of volume from people getting together to enjoy their lifestyle and companionship.
Oh and don't worry, they don't bite or bother anybody so don't be afraid.
I believe that is usually the first week / weekend in June. Before DS was in school we went down in early June to try to avoid the mid-summer crowds that peak after the northern schools get out and we hit that particular group. Large groups like that can really make for a lot of additional crowds but they do tend to stick together & all go to the same park on the same day. So if you can find out what their game plan is you can go to the other parks instead and avoid some of the overcrowding...
We have gone down a few times at that time of the year and it is very nice, not too hot yet and the crowds aren't too bad at that time either.