There is also concept of so-called viral-advertisements. For example - put some video on youtube with something "freaky", "sexy" or "funny" and put your product placement or "message" inside. Then promote that video in some loaded community on social network. Then your link will be spreaded like virus - people will send that "funny" thing to friends, post in blogs and so on.

There are uncounted examples of political statements packed into some music videos of marginal and pseudo-underground bands and the like.