OTOH, as was pointed out earlier, it looks like a chaotic, noisy environment. If you have that kind of environment, you may need to multiply your team size by 1.5, at least.
edit: from http://careers.theladders.com/ it looks like they are using Java, Spring and are fully enterprisey buzzword compliant (only missing an Oracle RDBMS). If that's the case, you can multiply your team size again by a factor of 3.
edit 2: talking with a colleague from another company (they do a lot of Ruby stuff) I could confirm that our two-week sprints (we do mostly Java in this cell) are too long for them. Your iteration time varies according to the tools you use.