Also, having too much of the same thing kills everything.
Just look at the numbers on some of these tourneys: 5 people, 6 people (picking some tourneys from 2009 here). There were just too many tourneys to care about them anymore. The highest number of participants I could find (didn't do an extensive search) was 27 (intermediate tourney). The average amount of players in a tourney in WO in 2009 was 26 (25 in the winter) - the first intermediate tourney I clicked on had 52 players, and it was 2v2, so some people probably didn't play cause they couldn't find a partner.