Spilling secrets about the bride and groom's last fling is a definite no-no. Revealing that the groom lied to the bride about going to a strip club for his bachelor party, or dishing that the bride drank too much in Las Vegas and almost got married to a waiter are just two details that shouldn't be discussed during any wedding toast. Or ever, really.
Take a cue from their wild and crazy nights, and avoid drinking too much before you make your speech. Too much bubbly gives you false confidence and blurs any censorship skills you might need.