i have been accepted via eamil, phone, and letter. i think it just depends on the program.
on the bright side, don't freak yourself out because other students have been accepted. i totally freaked when i heard other students were accepted to my top choice and convinced myself i was on the waitlist. i later found out i wasn't and my POI took a second student which was me, it just took a little longer for him to be certain the funding was in place. i never had any info from the school and i had just waitlisted myself b/c of things i read on SDN. moral of the story? stay hopeful and don't obsess over things you read on this forum (like i did )!