Patent buyer Intellectual Ventures can count Microsoft and Sony among its latest investors, but previous participants Apple and Intel aren't so in. Intellectual Ventures has previously taken substantial investments from many of the giants of the tech industry, and took that money to buy up patents and then offer a significantly reduced licensing fee to its investors for those patents. Those that didn't opt in to Intellectual Ventures' investment scheme could instead find themselves in the cross-hairs of a patent litigation suit if there was the slightest whiff of infringement. All of this even though Intellectual Ventures doesn't make anything or even patent things itself. You might call them a patent troll, and according to Reuters both Apple and Intel (companies with plenty of cash on hand) have decided that the cost-benefit analysis of additional investment wasn't in their favor.
Intellectual Ventures is going to take the investments from Microsoft and Sony and go out and buy more patents, which will be available for a light licensing fee to those too. Apple and Intel, meanwhile, having opted out won't qualify. In the 14 years they've been around, Intellectual Ventures has raised $6 billion and used that to acquire some 70,000 patents and other bits of intellectual property.