IMO: Heroku is a bad example of vendor lock in. To use Heroku, no code changes were required which would prevent it from running else where. A counter-argument to my counter-argument, Heroku limitations (i.e. 30-second HTTP request timeouts) required code changes for any and all web apps to work on Heroku. Anyhow, code that runs on Heroku can run anywhere.

Parse, on the other hand, was both the code and the infrastructure.

EDIT: p.s. love your newsletters!