DVI to HDMI cable: How long can they be without loss in quality?

Hi,
I am looking forward to purchasing my first HD projector which is to be connected **directly** to my MacPro computer.

Thus I assume the best way for a Mac to Projector connection is a DVI to HDMI cable.

I need the cable to be around 10 meters in length (32.8 feet) to be able to run it across the room, along the wall and into the projector.

Is this possible? Most HDMI cables I see around are 2 meters or up to 4 meters.. is there a reason for this?

Thanks for reading!
M.