The BTCC has them this year, the V8 Supercars uses them, the WRC uses them... do people like the idea?
It gives advertisers a greater space to put their billboards on, but does it add or take away from the asthetics of the series?

Personally I like NASCARs idea of big massive numbers on the door because notonly does it make it easy to see who is who, but it also gives a sense of identity to the drivers themselves.
I think of Richard Petty's 43, Peter Brock's 05, Dale Earnhardt's 3 and even Triple Eight's 888 as a few examples.

Personally I think that putting the numbers in the window looks stupid and takes away the sense of identity of the cars.