(See the comments for a lively debate about this idea!)
I disagree with the other answers here. (There are 5 at the moment.)
Like all good design answers: it depends. In 99% of cases, you'll want to put off on gathering information for as long as possible. But there are a few very good reasons you would want to collect information first. It all depends on your strategy.
If you're selling cheap, mass-market wines and you just want to sell to as many people as possible, then taking the information last approach is probably the way to go. Think amazon.com. You can do basically everything without logging in. This kind of structure works for a very general type of audience, since most people don't want to give out information right away.
However, if you're selling boutique wines to high-end clients, and you want to create a sense of elite membership, then asking for information first is pretty much required. This is how the mighty Facebook got it's start, and it's the model that sample sale sites like Ruelala and Gilt rely on. (They also rely on invitations, but if that works for your customers, it can be very effective.) If your site relies on word-of-mouth to get around, you don't even need to show them anything to get them to sign up. Look into private torrent trackers like waffles.fm. They even try to keep things secret.
But, from the sound of your question, it seems like you should go the more public route. I just figured I'd throw this out there.
** EDIT: **
Here's an article on why invite only works. Here's an interview with the founders of Gilt. (Read the questions from mid-page, by the book image.) Here's a view of these sites from a user perspective.
The important points in my eyes are:
- Users value their membership more.
- If they have a good experience, they will want to share with others.
- You have better control over your inventory.
To me, this really boils down to the kind of customer you're after. If you want repeat customers who are looking for unique items, special discounts, high-end items, etc... then a "membership" is the route I would take. But, if you're looking for mass-market, one-off customers who are just there to get things done, then put off info gathering as long as possible.