For anyone that read this and has a similar experience, it turned out to be an issue with our security group (specifically unexpected behavior as a result of combining multiple security groups).
I’m building an app that accesses the sample streaming API.
If I run the app locally (at my office) I receive various tweets and other events (such as Status Deletion Notices).
If I deploy the same code on to an EC2 instance, the stream comes up but I no longer receive Tweets. I do however still receive the Status Deletion Notice events. I will occasionally receive a tweet, but instead of the 20-30 a second, I’ll receive one or two per minute.