dp619 writes "A developer might fly under the patent troll radar until she makes it big, and then it's usually open season. Apple just shared that it has faced off 92 lawsuits over just 3 years. Even Google's ad business is at risk. FOSS attorney Heather Meeker has blogged at the Outercurve Foundation on what to consider and what to learn if you're ever sued for patent infringement. 'There have been at least two cases where defendants have successfully used open source license enforcement as a defensive tactic in a patent lawsuit. ... In both these cases, the patent plaintiff was using open source software of the defendant, and the patent defendant discovered a violation of the applicable open source license that it used to turn the tables on the plaintiff. In this way, open source license enforcement can be a substitute for a more traditional retaliatory patent claim.' Meeker also examines how provisions of open source licenses can deflate a patent troll's litigation and shift the balance in favor of the defense."