nchoosetwo and collaborative ranking

Walking around campus these days, there are cryptic-looking things like

\(\binom{n}{2}\mathrm{.com}\) and \(\binom{n}{2} \ni \binom{i}{u}\)

obviously referring to a dating site — currently it’s restricted to MIT and Harvard students. This one tries on an idea that I’ve heard discussed numerous times in different contexts, but apparently nobody went and did it in all these years. Instead of running a matching algorithm, it asks third parties (i.e. matchmakers) as well as the interested parties themselves to suggest matches. The thing that is supposed to keep this low-risk is anonymity: a match isn’t revealed until the two primary parties involved mutually accept or their lists intersect.

As with all things that involve anonymity, this asks for trollish and antisocial behavior. I’ve already registered three aliases on moira for exactly this purpose — ok, ok, so they’ve suppressed that antic after people raised concerns, though these and other ramifications should have perhaps been worked through a bit more carefully pre-launch.

The spam potential remains. A matchmaker’s identity isn’t revealed unless both people accept her suggestion, so pranks and insults can be conducted to an extent. One way around this may be grafting social graph data onto the system for collaborative filtering (if they manage to obtain such data…). And if they do, perhaps the suggestions of more closely related people should weigh more, along with those of successful matchmakers. Perhaps there should even be more weight if multiple matchmakers concur. This is extremely intriguing, because eliminating spam is equivalent to predicting who is a likely match, and collaborative filtering for this problem is an unexplored direction.

The more fundamental question is why such a site is even necessary.

Ostensibly, there is a gain over the serial nature of asking in person, due to the ability to make more informative decisions by using data you don’t have or cannot socially obtain in the open. If anonymity compels people to provide more preference information into the system than they would otherwise do, then everybody is better off. This is the positive aspect.

Nevertheless, if we wanted to use full information, why not run a global algorithm? If humans had no feelings, they could just make a list ranking whom they liked in order, and let a computer take care of allocation, almost like housing assignments. But alas, despite the rationality and efficiency of this obvious method, real humans appreciate neither the results nor the implications of it. Nobody likes to ponder the idea of not being #1. So something like nchoosetwo is a compromise, and hides the negative aspect of knowing too much: hurt feelings. But now the site becomes very dangerous. Under the cover of anonymity, the site is collecting ranking information about people from every action on the site. One particular situation in which an explicit rank order is elicited is where there are multiple matches. By your choice, you reveal to the system that “A is better than B.” Is this something the site should know? Not to mention that proposing matches in parallel, when combined with side information from the subsequently unfolding real world, also leaks preference information to an anonymous matchmaker. Those are much more dangerous information than who your Facebook friends are…

So far though, this site has embarrassingly few features. When you have a mutual match, all it does is to print:

Mutual crush! How about a date? ;-)

Tellingly, you can’t remove this.

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