I wasn't inconvenienced by it, but I remember myself and everyone at Dartmouth receiving a single email inviting us to join Facebook at the same time somewhere in the early winter of 2004. It wasn't a viral action like "your friend has added you", but was instead a direct invitation to sign up. I remember my roommates and I all immediately signed up and wasted the first of many hours on there.

I think the email was from another Dartmouth student, so I assume they just paid someone to send the entire campus an email.