[HAL9000]

they always warn you to remove it before sending your machine in for servicing since it will void the warranty

Third-party RAM does not void Apple's warranty.

[politicket]

Third-party RAM does not void Apple's warranty.

GASP!!! You're not telling me that the "genius" was lying to me, are you???? Oh, the humanity!!!!

[ReignOfError]

Third-party RAM does not void Apple's warranty.

In the past, opening the case on some Apple models voided the warranty. The oly current model I can think of where that would be an issue is the Mini -- and maybe the Macbook Air, but you can't expand the RAM on it anyway.