They do get pretty hot.
have u installed lion?? if so open activity monitor, make sure its showing all processes and look down the list for "usb print and storage centre" then end the process... 10 seconds later your mac will cool down and stop revving the fan up and down... also look to see if there is anything else running that is using a lot of power... anything over 100 that you aren't using close... (don't try and close a kernel process though)
mine started doing it soon as i installed lion... by stopping processes that are using a lot of cpu percentage it stops the over heating...