I just got a Facebook friend request from someone at my work whom I've never met. I don't even know what she looks like, but I've seen her name in email threads. If this were LinkedIn, I'd easily confirm, and I'm totally fine with friending folks at work when I've at least had a one-to-one email exchange with them. I can't see her photos unless I confirm, so I still don't know who she is or what she looks like. Once I do, I'm worried I'll be scouting the office for her face, awaiting that first awkward encounter in the elevator or by the coffee urns, confused about how to start the in-person introduction. So do I confirm? And when I do, do I ignore her and let her take the lead in introducing herself first?
~Urn My Friendship
If your bar is at least one email exchange, and that's a mighty high bar indeed, then send her an email. It doesn't have to be lengthy, or even inspiring. For instance: "You Facebook friended me, but are clearly not hot enough to be memorable. Remind me who you are again? I'm the chick with glasses from HR, awkwardly awaiting our chance encounter at the coffee urns."
If you choose to simply accept her FB friendship, then presumably her pictures will show up and you won't even have to bother guessing, unless she's one of those artsy types with all pictures of her feet overlooking a craggy beach or something. Or if she wanted to "promote child abuse awareness" by changing herself into a Strawberry Shortcake avatar. Then you'll be screwed and have to email her anyway to unlock the great mystery that is her face.
In terms of whether to introduce yourself in person or not, that depends on how much you give a shit, generally. Some people are quite chummy with their coworkers; others merely exchange pleasantries and move on; still others say absolutely nothing to you at all, leaving you to have one-sided conversations with yourself about how sometimes while falling asleep, you wonder what Luke Perry is up to, but more importantly you wonder if anyone else has those same thoughts, and yes, you are having peanut butter again for lunch. I tend to friend coworkers and then forget about them entirely on Facebook because we see each other all day every day and I already know who among them will not be scared off by my many references to the "wang arts" and therefore don't need to repeat myself electronically.
The only reasons to not friend a coworker are if you think she's a potential mole hired to sniff out those among you who are, as we say in the wang arts, mixing business with pleasure. Or she is your manager or boss. If she's neither, then friend away. And don't worry too much about your real world meeting. It probably won't be any more awkward than seeing her twelve-year-old sequined American flag jacket photos from Glamour Shots on Facebook. Hypothetically, of course.