For my 2010 MacBook, I ordered a 4GB stick of ram to replace the two 1GB sticks that it came with. Will I have any issue using just a single 4GB stick of RAM while leaving the other memory bank empty? Thanks.
Shouldn't. Might affect dual channel though, not having the "ideal" identical (2+2) sticks in both. Not really sure. It wouldn't be noticeable anyway with the increase in speed that you would experience as a result of the doubled-RAM.
You could even go higher on the memory if you wanted to.