Right, I'll go first.

 A wedding is a social event like any other, so therefore a perfectly acceptable place to pull. There are also likely to be a fair few single members of the opposite sex, whom you haven't met before, and who are often easily identifiable as single (who goes to a wedding without their partner?).

There is also a rumour (generally among the female populace) that a wedding is a really good place to meet your future spouse. I think this is a bit of nonsense put about by desperate over-30's single women, or unscrupulous males who want to take advantage of them. How many couples do you know who first met at a wedding? 

This brings me nicely onto the lingering air of commitment. Again, a wedding is no different to any other social occasion, and the sight of seeing their best mate getting hitched is unlikely to make Jack or Jill the Lad any less inclined to vanish after breakfast. The rules are the same as in the pub or club; if you meet a nice chap or lass, have a snog and get a number. If they really like you they'll make the effort to see you again.

Impropriety – it's probably not a great idea to pull the bride's sister (or Mum, or Gran), but any guests who aren't likely to be on the top table are pretty fair game. Although going for it in the toilets is probably a bit unnecessary.

As for the free bar, this is surely as much of a hindrance as a romantic lubricant? Or maybe that's just for those of us who have no idea when to stop…

I think by "randy" you mean "desperate"

"Nice buttonhole"