Just some thoughts of both effects: First, I never saw the term Hydra effect before. Love it. In this case Hydra is more accurately describing the situation here, especially with Open Source. Because each time you kill a head, new one spawns as a fork. Streisand is not necessarily that, that is more about hiding information that results in more people looking at it and have an interest because you hide it. Hiding makes it interesting (why kids love doing stuff they are supposed not to). Off course both effects are appropriate here.

Does anyone know any other effect comparable to these?