Ligers-Myth?

Are ligers a myth, or are they real?  I have heard many times that ligers do not exist.  That statement has always frustrated me.  Unlike the sasquatch, or the yeti, ligers have been seen and are proven to be real.  Believing in the sasquatch is okay, but saying that ligers are fake is just flat out wrong!  Saying ligers are fake, is like saying elephants are fake! That's crazy!