In US law, I'd think the more relevant precedent would be US vs. Microsoft. Judge Jackson wrote a lengthy decision procedure for when a platform is a monopoly.

In US law, I'd think the more relevant precedent would be US vs. Microsoft. Judge Jackson wrote a lengthy decision procedure for when a platform is a monopoly. Microsoft's position was that Windows is not a monopoly, because customers had the option of buying a Macintosh instead of a PC. Jackson threw that argument out (and Posner let that opinion stand in appeal, IIRC). I think this is the relevant bit. http://www.justice.gov/atr/cases/f3800/msjudgex.htm#ii http://www.justice.gov/atr/cases/f3800/msjudgex.htm#ii IANAL.