oh so you're a photographer

Don't ever do a wedding, even your best friend's. Only do it if you are a wedding photographer and are being paid, and preferably don't know the couple too well.
Say no if your friends ask you to be the official photographer. You won't enjoy the wedding at all, as there will be too much pressure to be out snapping. If the pics turn out badly, and they often do, they'll be a simmering source of resentment for decades.
Take your camera, enjoy the wine and get some great shots but leave the pressure of doing it right, to someone else.
Well that's my two cents.

Proger - having never done a wedding, my outlook is the same as yours. Took a few informal shots I was happy with at my Mum's, but wouldn't want to have done any more. A couple of friends were going to ask, then got me to DJ at the reception instead - still stressful, but much more fun.

Oh, I got paid (and it's the third one I've done for which there was payment or payment-in-kind) and they've all turned out OK. The couple were ultimately delighted with the 230 shots I whittled the day down to. I've got a (small) bottle of rum from their Mauritius honeymoon on my desk as extra thanks!

Yes, there's definitely an argument for leaving it to the pros (and I've said as much to three couples in the last two years who made enquiries regarding my services); this time around the couple very sweetly said that they'd "only be asking the pro to get photos that look like (mine)", so they hired me.

I do occupy that grey area at the moment where I'm good enough to charge but not top pro rates. I look at the work of a colleague who runs a wedding photography business with his wife and I think I'm some way short of that. The greater leap is not in terms of quality of work but in terms of attitude and selling yourself and dealing with several dozen strangers on the biggest day of their lives. It's only been friends/colleagues so far.

(And I've just been offered another one. Erk...)

being paid can help nudge it a bit more into "good idea" territory. just be sure to check and re-check every conceivable setting on your camera! and bring an extra camera! and have a friend help out too! these are things I've learned.
my friends paid me to do their wedding. basically enough to be able to fly out and attend, plus some spending money. since it was on the other side of the country, their offer was my only chance at getting out there anyway, so it was kind of a no-brainer (I never really have enough money for travel).

This just happened to me.

A coworker's due to be married in a month, and she just asked if I'd like to shoot it. Gave a tentative yes, but I'm still not sure how I'd feel about charging for what may turn out to be crap (nor do I have any clue what a fair rate might be).

OTOH, it'd be a fun day's challenge. I think part of the reason she's even considering me is that most wedding photographers I've seen in Seoul tend to be obnoxiously intrusive.