scottie on 16 December 2008
I would argue it's not related to a particular percentage, but to what it means you can do.
MS has just under 90% market share in the OS market, and yet I wouldn't consider it a monopoly due to a lack of two main things
The ability to drive their competitors out of business if they wished (and believe me, they are trying their hardest to stop people turning to Linux or Mac)
Creative control over the direction and pace of advancement of their industry
