Hell yes. The benefits for the users alone is enough to warrant this. When I purchase a piece of hardware, I have to do a lot of research to find out if it works with my OS. If it says "linux" on the box, I get to wonder how much programming / hacking I'm going to have to do and how many dev packages to download and what kernel version I'm going to run before I can use the device, although I'll probably eventually get it to run, the time it costs me may be as much as the hardware's price tag.
Having hardware compatibility lists for printers, scaners, webcams etc. stating whether there is a driver (even a proprietary one) would definitely reward both the manufacturers and the users.
"Works with Ubuntu" is as vague as "Works with Vista" (read recent news...) - the list should discriminate between "plug and play", "minor work needed" and "complex workaround needed".
I bought a Nvidia Card with my new PC because it is the best supported 3D Card for Linux. :D
If the ATI OpenSource Driver was ready to use and good functioning, I would have bought an ATI GPU. ;)
But I think the Suggestion for a better Hardware Database is what could do the Job of rewarding the manufacturers.
http://brainstorm.ubuntu.com/idea/40/
So support that suggestion if you liked the Idea of this Suggestion. ;)
If there's money for that, it should be used on programming for drivers. As Ubuntu users grow hardware companies will want to provide drivers for Ubuntu.