I am afraid you are mistaken. The number of people who know Polish around here is about 40%. This proportion is largely due to the fact that this site is also a contest hosting service, and about 500 students from the Gdansk University of Technology use it regularly. Though these contests are technically concealed, some problems from the main archives are reused, and a few people choose to solve them in the main stream of the online judge rather than in the respective contests.
Take a look at http://spoj.sphere.pl/ranks/; Polish users in the top 200 are the largest group, but by no means dominant.
