To be fair, I've not actually played much with the VoD ones other than flick through the libraries and see if a couple of streams play. There's every chance they do break playback to throw adverts at you, I honestly don't know.
The live-tv streaming apps I've seen didn't seem to break for adverts, but I could be wrong. I don't have a box at home to play with or test so it's all passive observation.
Even so, does advertising revenue actually work out profitable after running costs?