I dont know if this could be developed easily - I imagine it could work something like Map Rank.
The tool, if created, would show a players most common opponents, teammates and both, in combination (perhaps, along with +/- points totals with these players and a link to common game history).
This would be really useful to players wary of dodgy alliances, mods wishing to investigate them and tournament organisers making sure they group players 'safely'.
What does anyone think?