Originally <a href='/showthread.php?p=18170776'>posted</a> on 03/21/2013:

Well you have exchanges (matchbook & betfair) that act as market makers and take a commission.

What I think you mean is lines maker? I don't know the operation of books but usually Pinnacle/BM open most US sports numbers and SBO/other asians books for soccer They limit openers to sharpen lines before raising limits afterwards. As to who sets openers I think they employ handicappers in house(consultants) but at one time Roxy Roxborough and Las Vegas Sports consultants set the lines used by most books until they moved offshore.