yes there are equal amounts of shares bought and sold...but if demand exceeds supply then the mm would sell out of his inventory or if supply excceeds demand then the mm would add to his inventory...thus creating a buyer for every seller...that's why the bid/ask on thinly traded stocks is percentagewise so large...to compensate the mm for his inherent risk...but there is only so much a mm can do to match trades...frisbing stocks still should have a net zero effect on sp..prices change on supply/demand so when you have an equal amount of supply demand ( frisbee trading ) should have a net zero effect on price