i never rate an image anymore for the same reason.  Maybe a voting scale with clearly defined criteria published somewhere... and yes a 1-10 scale would possibly make it better.
1-"snapshot" with no merit at all.
5 - decent but some problems with lighting/composition - room for improvement
10 - i would pay $30 (£15 =P) to have an A4 print of this on my wall.

And maybe a system where people who just vote 10s all the time are punished by their vote not counting as much.  I have been on the Worth1000.com site for a while now and they have a "karma" system which basically gives your vote more power based on how fairly you vote.  Not sure if the rosity elves would like to code that in tho. 

"In every colour, there's the light.
In every stone sleeps a crystal.
Remember the Shaman, when he used to say:
Man is the dream of the Dolphin"

Rich Meadows Photography