To begin with, it seems that everyone supports wish lists, but since everyone does it differently and as there is no interchange standard its not very useful. It doesn't do you any good to know that I have a think geek wishlist, if you are shopping on a different site even if they have things that I may want. So, the proposed site will have a wish list but will explicitly let it be exported, downloaded, or queried from another site. The thing will talk standard XML and it will be well documented. If possible, it will be based on Amazon's wishlist output format (although it may need extending for some of the ways we'll want to use it).
Lets not stop there though. Letting others easily browse the site's wishlists is only half the battle. There would also be a need to write a number of query tools that were capable of fetching wishlists from other sites and reformatting them for local use. In fact, one should be aiming to bootstrap an entire distributed wishlist database system, spread out among as many merchants as wish to participate.
Once the various wishlists are available on site, they can be used in two different ways. First of all, they will allow for the modelling of the desires of a particular consumer, especially if using wishlists from several different specialty sites. This will allow for the selection of items that aren't specifically on the wishlist, but which may be desirable. Secondly, the site can happily buy items off of wishlists from other websites, charging a commission for having done so. The convenience to the user of having only one place to go to shop for gifts should make up for the added cost.
Since the site will cater to convenience, it should also try to make sure that folks who register with its service don't forget any birthdays, anniversaries or other special occasions. Not only should there be a calendar on which they can record who they need to buy things for and when, it should also happily interoperate with other systems, like Yahoo's calendar.
When a special occasion is near, an email can be sent with a gentle reminder and an URL to click on to go to a customized selection of possible gifts for the recipient. If there isn't much info available on that person yet, the gift selection will be whatever seems popular, but the system will take note of what choices the buyer makes, and may even request feedback later. The user will be encouraged to add notes about certain categories of items that a person does or does not like.
There would also be a system set up to allow someone to request random reminders to do something thoughtful for a friend or loved one. These will also come with suggestions for gifts that that can be as simple as a surprise gift of gourmet cookies, or a complete night out including a limo, reservations at a restaurant and theatre tickets.
There could also be way to set up a layaway plan for paying for expensive items slowly. If a user has their credit card charged by a set amount every month, they will be able to afford that ruby pendant when the big anniversary rolls around.
Finally, if someone has set up one of these advance payment options, they could be asked to be given gifts off of their own wishlist. Depending on the choice of the user, they could get the gifts at set intervals or at random times, they could receive the next highest desired gift on their list, or one at random.
One temptation that would have to be avoided when setting up a site like this is not to automate it too far. Only in the case of a person asking for a gift for themselves is it appropriate to completely automate the system. After all, a gift is supposed to show someone that you care and are thinking of them. An automated system that you could sign up for that would be able to remember birthdays and send out gifts without any user interaction would completely defeat that. If the site were to get the reputation of catering to the cold and uncaring who merely wish to appear to care, public opinion could kill the venture.