Remember how fun it was to stack Legos when you were a kid? What's that the same sort of scalablility concept beneath the Bloom Energy "box."
Right now, a single fuel cell can power roughly a lightbulb. Want more electricity, build yourself a cube on up to a parking-space-sized server. See for yourself with this ZDNet video about the launch.
If you didn't read my post about Bloom the other day, here's more background on the company's concept of distributed energy (as opposed to distributed computing).