Is there a way to run simulated traffic to determine how your server will react based upon heavier load to try and determine how many people it can serve?
[1] http://news.ycombinator.com/item?id=4847949 [2] http://www.joedog.org/siege-home/ [3] http://httpd.apache.org/docs/2.2/programs/ab.html
Addendum: Oh, load impact is pricey though.