I have found that the MAJOR disadvantage of 
keeping the tape on the background is that over 
time, the tape turns yellow.  :(  When you try 
removing the tape at that point, (or even if you 
don't you can still see this) the paper turns 
yellow where the tape was/is.  I had a cel where 
that happened and it really bothered me.

The only advice I can give on removing it is to 
DO IT CAREFULLY!  If you find that removing it 
makes the paint or paper peel, then you could 
wait for the tape to get older so that it's 
easier to peel (but you run the risk of yellow 
tape/paper as well).  

I ALWAYS remove the tape from backgrounds just 
because I hate those yellow stains.  ^_^;

jINx