It looks like Microsoft quietly relaxed their Windows Phone hardware requirements late last month, as both Twitter source @MS_nerd and the official MSDN page indicate. Manufacturers no longer need to include any camera on their device at all, as these parts are now listed in the “Optional Hardware” section along with the gyroscope and magnetometer (compass) sensors.
Cameras are your standard features on smartphones these days, but sometimes to cut costs you need to remove “unnecessary” features like the camera. Maybe Nokia plans on targeting super-low-end and ultra-cheap markets with camera-less Windows Phones? There is also the possibility, as @MS_nerd points out, that having no camera on a Windows Phone might meet special government/enterprise security needs.
As it still stands, Windows Phone requires a standard set of buttons, WVGA (800 x 480) display, cell and Wi-Fi connectivity along with at least 256 MB of RAM and at least 8 GB of storage. Rumor has it that the upcoming Windows Phone chassis revisions with the “Tango” and “Apollo” updates will bring extra features such as 480 x 320 and 1280 x 720 displays, LTE 4G connectivity and dual-core processors.
Somehow it seems unlikely that Windows Phones without a camera would sell… at all… but at least Microsoft are giving manufacturers the option to save money and remove them.