Actually, the issue is going to be with the power load: it takes a hefty PSU to power more than one mobo, especially if it's crunching.
So...
http://www.procooling.com/articles/h...ween_psu_s.php
Which I adapted to make a redundant PSU array (still under construction, linked in my sig).
A more sane person than me would simply use cheap small PSUs for each mobo. More sanely, you can have one very large power supply for each voltage rail (+12, +5, +3.3, -5 and -12), but the bunch of smaller PSUs is still going to come out cheaper.