Dave,
Pretty much the same thing happened to me a couple years ago, at one of the first weddings I shot. Same story—avid amateur photographer friend of bride has asked bride if he could come and take photos. I did talk to him beforehand and tried, very nicely—I'm a nice guy and not pushy—to explain my "rules" (basically, stay out of my shots and don't get in my way). He agreed. I also asked him to come to the rehearsal so we could talk a bit more and perhaps do some coordination in advance.
He didn't come to the rehearsal. That should have told me something.
At the wedding, I did ask him to shoot from the other side of the church, and that worked okay.
But after the wedding, while I was trying to shoot formals and deal with moving people on and off, the bride disappears and then I see he's pulled her aside to do a portrait of her. That's when I really should have pulled HIM aside and had a brief chat.
At the reception it got worse. He's in quite a few of my photos, including some that would have been much nicer without him.
*
I understand that these days, 2 out of 3 guests have SOME kind of camera with them at the wedding, if it's only a cell phone. 1 out of 5 seems to bring something better than a cell phone. Some of these photos DO show up online very quickly, because the takers go home, and I think some of them just upload the files straight from their camera. Somebody here posted very recently about somebody else (may have been the videographer) who was either selling prints or showing a slideshow of photos taken minutes ago, while the reception was still in progress!
I also understand that it's my job to make sure that MY photos are much better than those taken by the amateurs.
Still, I found that experience very frustrating and I work now to avoid a repeat. It's not the real amateurs that bother me. It's the enthusiast friend. It's much easier to take one or two good photos when you are attending the wedding without any real responsibilities. If you miss the kiss, or the vows or the bouquet toss, or whatever, it doesn't matter, because you weren't being paid to shoot them and in fact you had no obligation to shoot anything. So you can stroll around and just take the photos you feel like taking.
That would be fine except when the enthusiast starts to compete with the pro. That one time a couple years ago, I found it rather distracting.
*
In the end, this may be a problem that has no simple solution. So many people have cameras you simply can't control who is doing what. You and I were both asked in advance. But now I find that there are folks at weddings with DSLRs who are simply going around and taking their own photos and don't think to ask me or the bride. There's nothing you can do about that.
Bottom line: You have to be better than the amateurs and the enthusiasts. If the bride has to wait for your photos, you have to make the photos worth the wait. In my case, I've started hedging my bets by (a) continuing of course to try always to make my photos better than any amateur's but (b) by getting "proofs" online very quickly, within days of the wedding. I think this is critically important now. Clients have no patience, a limited attention span, and if I can't deliver photos for weeks, well, by that time the wedding is old news, at least for some of my younger clients.
Will