The opportunity costs are just too high not to go stag at a wedding.
Outside of an ounce of pre-booze loneliness (Mssrs. Jack Daniels and Dom Perignon almost always skip the ceremony), I can think of no single reason to insist on bringing a date to a wedding (outside of a decent chance of hotel sex). Sure, a crass uncle may think you're gay (ladies can be gay), but he may think doubly so when you introduce a date as just a friend—and who cares what that pederast thinks anyway?
That said, sometimes (like in a Julia Roberts film) you are absolutely convinced you can't go solo. That's when you have to fall back to this checklist:
-Are they unbelievably fun to be around?
-Do they dance?
-Are they at least an eight in the looks department or (if a man) a 9 in the humor department?
-Will they possibly put out (remember hotel room sex?)? If not, are they a talented and selfless wingman/woman?
-Are they willing to chip in for travel and/or a gift?
If the answer to four out of five of these is a resounding "yes," feel free to invite your buddy... or pay a relative stranger. That said, a young actor in New Jersey is looking for a wedding date and has put together a funny website to accomplish his mission. Godspeed, young actor. Check out DateSatch.com and see if you have what it takes.
* Or some surrogate equivalent if distance, death or maximum security penitentiaries prove tricky.