How many multisite installs are out there, anyway? In a recent forum post unrelated to multisite but using those numbers for comparison, Jane gave some numbers:
We can’t really get very accurate stats, because we only know about *installs* that phone home, not number of users on each one who might need the multisite menus. We know of about 60,000+ multisite installations, half of which have more than two sites. The average is 58.7 sites per multisite install (that gets us into the 3.5 million sites mark, times however many users per site). Then, 31 installs have more than 10k sites. Edublogs, for example, has over a million sites. Universities like CUNY have thousands/tens of thousands of users per install.
And a bit later:
Better stat courtesy of @nacin:
“Chop off the 31 sites > 10,000 sites, chop off the 30,000 sites <= 2 sites.96.3979 average for the remaining 30,000 networks."
I actually talked to Nacin about these numbers back in July at WordCamp Montreal, so these stats are not surprising to me. Seems a little low though – what do you think?