It doesn't make sense to make this personal. Business models inevitably change when startups grow up. You can't expect a company that needs to create network effects to act exactly the same as one that needs to exploit them in order to make some money and pay back investors.

Twitter got the funding to build that massive infrastructure only because someone believed that they would eventually be able to monetize it. Twitter is not a public utility and everyone knew it.

The conclusion isn't to never use something one particular guy does. The conclusion is this: If you build on someone elses infrastructure, make a contract or make sure you exit before the tide turns.