There seems to be a lot of confusion over whether guests should bring wine, and what should be done once the vino is proffered.
Let's straighten this out, shall we?
It's nice to bring wine, whether or not the host asked. As a host, it's okay to have a BYOB party. Keep reading to know what not to do in both sitches.
For the Guest
Scenario #1: You're invited to a dinner party. Host has asked for nothing, but you bring a bottle of wine.
First off, good on you for the nice manners. A certain etiquette columnist scoffs at the idea of bringing wine as "admission" to a dinner party. I don't think anyone thinks of it as "admission," merely the right thing to do.
Didn't your mom ever teach you, "never show up empty handed"? If she didn't, you should have at least heard this from Deepak Chopra.
When you're a dinner guest, it's nice to bring something--dessert, wine, even a nice card. Conventional wisdom says, "don't bring flowers -- it's extra work for the host!" but I disagree. I love flowers, I love people who bring me flowers, I love bringing my friends flowers.
For the Host and Guest
But back to the wine. When nothing was requested, the good host will thank you, and perhaps put it out, or she may set it aside. It's also nice if the host asks, "Would you like me to open this now?" The proper response is something along the lines of, "Whatever you want." It's rude to make a host feel like she HAS to open and drink your bottle right there. Besides, what if she's a recovering alcoholic?
If you're the host, never ever do what Jan on "The Office" did and say, "Oh, good, we'll use this for cooking."
Also, if you've brought wine, do not, under any circumstances, ask for or take it back at the end of the night. It's classless, and looks cheap. I once hosted a dinner where we could not open all the wine that was brought. I was once told by one guest, on her way out the door, "Go ahead and keep the wine." Um, yeah, I was planning to do exactly that.
For the Host: BYOB Parties
Scenario #2: You've indicated your party is BYOB (acceptable) and everyone brings wine.
Leave it out for partygoers to enjoy.
I once attended an engagement party where we were told on the invite, "Bring wine or presents." Okay, demanding anything is rude, but I played along and brought a nice vintage. I arrived, handed my wine to the host, and watched as she promptly turned and stowed it in her liquor cabinet for her personal use. Rude.
So, got it? Bring wine as a nice gesture; as the host, leave it out. Good.