I think a competitive game in year 2013 really needs a matchmaking system. The new system in LoL is really fun.
This is how it works:
http://na.leagueoflegends.com/news/new-league-system-coming-soon-ranked
Long story short:
At the start u play 5 games, which decides the bracket/tier u will be matched to. U start with some points, losing games = - points, winning games = + points.
If u reached 100 points, u have to play best of 3. If u win 2 games, u get promoted to the next higher tier. Losing best of 3 = u have to start collecting points again.
I think matchmaking for competitive gameplay is great thing, if u want to play some comp. games, but u dont want to join a clan or look for members. Or u just want to play some “serious” games after your working day, with just some clicks.
This would only work for shooters if u can communicate via VOIP ( see Steam ) or else.
Of course this also means, if a shooter for example offers you a solo-queue: Its always a risk if you will be matched with some nice dudes or some trolls. ( Just lik it is in LoL).
The consequences of a matchmaking-system would be system that can report/ban players, which I guess it a lot of work. Which is in my opinion totally worth it.
Another way to get to matchmaking would be: Offer leagues like the ESL an API to connect their versus system and Dirtybomb. This could also be a good benefit.
ESL “Versus” - Matchmaking: http://www.esl.eu/eu/versus/