I know a few, at least one asserted one of their few patents against IBM to force a licensing deal -- reversing the direction of the money to the startup instead of them paying IBM.

If a startup has some decent patents, they get to have a conversation with companies like IBM that come calling. Otherwise, they have to roll over.

Basically, when the IBMs of the world come around demanding a license, you show IBM they are infringing on your patent.

In general patents are business assets or business tools. They are important for valuation, among other things.