Lives change -- often forever -- after an engagement ring is exchanged. And no one is happier about that than Blue Nile (NASDAQ:NILE). The online jeweler has carved out a cozy living by selling high-end diamond engagement rings to nervous grooms-to-be.

Getting hitched is big business. Just check out the folks streaming in to Williams-Sonoma (NYSE:WSM) or Macy's (NYSE:M) to fill out bridal-gift registries. Log on to The Knot (NASDAQ:KNOT), where more than 3 million unique visitors scroll through the site on any given month, in search of advice and leads on local wedding-service providers.

And what's a wedding without flowers? That's where companies such as FTD (NYSE:FTD), 1-800-Flowers (NASDAQ:FLWS), and even Martha Stewart (NYSE:MSO) come in, with seasonal blooms to spruce up reception halls, table settings, and the flying bridal bouquet.

A simple nod sets it all in motion, but you need to get the engagement ring first. Blue Nile -- a popular Rule Breakers newsletter recommendation -- has excelled on that front. But will the shares jilt investors at the altar? The stock has certainly had a great run over the years, but has it come too far, too soon?

Not all Fools agree. Billy Fisher is bullish on the company. Chuck Saletta is our bear.

Which proposal will get your nod of approval? That's what this week's bout is all about.

Duel on!

Blue Nile and The Knot are picks in the Rule Breakers newsletter service. Want to get hitched to better growth stocks? A 30-day trial marriage can be arranged, for free.

Blue Nile is also a former Motley Fool Hidden Gems pick.

Longtime Fool contributor Rick Munarriz regrets that Blue Nile wasn't around when he had to drive all over town to find the right engagement ring for his eventual wife. He does not own shares in any of the companies in this article. The Fool has a disclosure policy.