Q: Trying to add memory to iMac mid 2011 - site says to pull on tabs to get memory out but won't come out

Pull it hard. Sometimes it is quite difficult to take the RAM out of the slot, but it gets out after pulling hard. See > http://support.apple.com/kb/HT1423?viewlocale=en_US&locale=en_US#4

This can be quite difficult since "gently" usually doesn't work. You will need to pull pretty hard, gently rocking back and forth, but being careful not to tear the tabs which will only make removal harder. If you have no success or tear the pull-tab, then you can coax the modules out by carefully gripping the edge nearest you with a needle-nosed plier. It's a good idea to use some sort of cushioning between the plier and the module edge so as not to damage the modules.