This is a nice list, and I've used most of the services myself to get small projects going. It's really great how you can quickly get a project off the ground for free, and then only start paying if it really does take off.
However, this is one of the problems with all of these services, they are very expensive. Once you do need to start paying for them, they quickly become much more expensive than investing a little time into running your own servers, at least that's the case with Heroku, MongoHQ, and Amazon S3. I always like to remember that my project is not a 'Heroku' Node app, for example, it's a Node app that happens to be deployed on Heroku now, and needs to be deployable on something else in the future at short notice.
Agreed, these are very expensive once you have to start paying for them. But good, nonetheless, for getting the MVP out and start getting some traction.
However, this is one of the problems with all of these services, they are very expensive. Once you do need to start paying for them, they quickly become much more expensive than investing a little time into running your own servers, at least that's the case with Heroku, MongoHQ, and Amazon S3. I always like to remember that my project is not a 'Heroku' Node app, for example, it's a Node app that happens to be deployed on Heroku now, and needs to be deployable on something else in the future at short notice.