Any camera can be blocked, and as noted, the one you've got "manned" should always be on the "money shot", and shot as if no others were rolling... but more than once I've been saved by having a "second angle" in mixdown.

I trust my settings, framing and camera positioning - it may not be as dynamic as a good cameraman, but there's one less "thing" to go wrong... human error (the "theme" of the thread, and it's happened before...) is the "highest risk", IMO. Unless I completely forget to start all the cameras running (flash, no more tape for me!), I've got at the very minimum a wide shot from the rear to work with... but as I say, I've got the "template" in my head, all I need is to hit the venue and work out the placement.

I've got good steady tripods as well as discrete mounts - setting a small camera at an angle you know you want but probably wouldn't be able to get otherwise works for me. I've clamped cameras to railings on a riverboat... my "kit" isn't overly large or heavy, other than the tripods, but it's prepared for mounting cameras discretely and effectively as needed. Also I set everything up (camera and accessory wise) in a hard case, so everything comes out fast, and loads back up fast as well.

actually, I"m much alike many other single shooters here that use a lot of unmanned gear, whether they are camera's or audio devices. We all take controlled risks and only can hope for the best.
The only way however to be sure the errorrate is limited to a absolute minimum is to have every camera you use manned and to have a dedicated soundguy who does live monitoring and of-course have a communication system in place so you can talk to eachother for directions. But as said, this is a luxury most of us don't have because the client won't pay for it, fact that we still under these circumstances use risks just to make our recordings look almost as good as the real thing says a lot about how serious we take our job. But it cannot be denied that the risk of making mistakes, or by lack of time, or by lack of control will always be a factor to take into consideration.

18 years of wedding videos and I worry about that little red button every time.

I always take the couple back into the church after the dust has 'settled' on the out-the-front-of-the-church stuff and get them to re-enact the putting on of the rings which I shoot as an extreme close-up. I then edit this into the main footage.

Although I must admit that from an editing point of view this is a very clever solution to bypass the limitations of a one-camera recording as it will give you the possibility to shoot from an angle that otherwise would hardly be possible. And if this stays as a "secret" between you and the couple nobody will ever now and always be asking how on earth you managed to pull off such that shot. :)

But...I think it's just me but I never would do such a thing, sometimes you see when they slide on the rings that it's difficult to get the ring on and bride/groom getting nervous or starting to laugh, when I capture the ring part I film them waist up so you can see that they are putting the rings on and even if I can't get a clear shot of that, that doesn't matter to me, it's their reaction, their face expression that counts. If I would redo such a shot afterwards focusing on the rings (and with intention to get an extra point of view) you will notice that it's not filmed at the same moment, it will show that something is not right.

In this case the "creative" shots comes second for me, then I just want to record the emotion as it happens. Only if I would notice that for whatever reason I did not get the ringshot at all, only then I would do what you do just to have something.

I agree with Noa, anyone who's worked on demonstration programmes in a studio knows how hard it is to do accurate cutaways - and invariably ends up putting in an extra camera to shoot the whole thing in one go.

Here's our trick (OMG why aren't I charging for this? ;) )

Most people put on the wedding ring (assuming it's not a heavily stoned affair) on the other person holding it North-South with the thumb at North. It's natural and easiest because the receiver's other fingers are limiting access at East-West.

But I always explain to my couples how difficult the natural way (N/S) is for me to shoot - and ask them if they'll try and remember to hold the ring from underneath in the East-West position. This means the giver turns their hand through 90 degrees clockwise from the natural position.

I explain that I realise that they'll have a few more important things to think about at the actual moment but that if they can give my wife and me a couple of seconds of their thoughts, it'll give us the best chance of capturing forever the ring actually sliding on. As far as the limits imposed by the other fingers, in reality most rings only slide up to the second knuckle anyway.

It sounds unlikely but I tell no lie when I say we have a 90% success rate - and the other 10% we get in a waist up shot from our third camera zoomed in from the rear of the church, but that's another story!