An interview with Nintendo Europe reveals some intersting things about how the DS will go online.
Correction: Jim Merrick did specify that buddies could be added online as well, but didn't go into as many specifics.
At the German Games Confrence, French website Puissance-Nintendo tracked down Nintendo of Europe's man in charge of marketing, Jim Merrick. Merrick was asked about how exactly the DS Wi-fi connection system would work, and the answers he gave in return offered many new details. Normally, the site would be all in French, but figuring the information extracted in the interview was of some importance, they were nice enough to offer a version translated into English.
One of the first points touched on in the interview was about how the match-making and buddy list system would work for the DS. Merrick re-confirmed that it would completely free (unless third parties wanted to charge for their own services, such as for MMORPGs). As for playing with others online, you can choose to play only with your friends, someone of any skill level, or select to be matched up with people of a similar skill level to your own. The interface will vary depending on the game, so it matches up with the game's presentation instead of just using a GameSpy template.
The process of adding people to a DS buddy list was also explained. One specific way Merrick said that a buddy could be added is to simply go to someone they know with a DS, and add them locally. The system uses a complex way of generating a special password or key to grant buddy access. However, a player would never see the confusing stuff. In terms of how simple it would be add someone else, Merrick explained, "it's really like sharing your phone number with somebody."
Another point touched on in the interview is how DS network servers would handle registration. Upon connecting for the first time, the network server assigns a unique ID number to an individual DS. After that, players will be free to choose any username they would like for each individual game, including duplicate names of other people already on a particular game's server. Said Merrick, "we know people want to be called Mario when playing Mario Kart, or Tom Nook when playing Animal Crossing. And what the developers have asked for is the ability to have names in context of the game. So you might be Mario while racing a Mario Kart game, and Tom while playing Animal Crossing, so you don't have to pick one name for all games."
This point also brought up a web interface. The unique DS ID can be connected to an account on nintendo.com (or nintendo-europe.com for the Europe folk). From the Nintendo website, you'll be able to manage a buddy list, high scores ranking and other information from a computer. No other information about this particular service was mentioned in the interview, disappointingly.
If you want to read the whole Jim Merrick interview with Puissance-Nintendo, which also briefly talks about Mario Kart DS and Animal Crossing DS, click here.