wordpress.com isn't funded by fees ~ http://codex.wordpress.org/User:Matt/WordPress_Inc_Story

It's all self funded even the hardware. There seems to be lots of confusion about this. Not the least this article ~ http://www.airbagindustries.com/archives/008169.php

Wordpress does pass around the hat for donations but I don't think that would be classed as a good business model.

'... Almost everything on WordPress.com is free, and things that are currently free will remain free in the future, but we do offer paid a la carte upgrades for things like CSS editing and custom domains. How do we pay for everything? WordPress.com is run by Automattic which currently makes money from the aforementioned upgrades, blog services, Akismet anti-spam technology, and hosting partnerships. ...' ~ http://wordpress.com/advanced-services and http://wordpress.com/about

stands corrected. Looks like there is more than what first appeared. I notice they don't advertise this much.