technically I don't think these services are allowed anyways. It would depend on how Mojang has their EULA written, but if you force a user to go through a ad-based site to generate revenue off the download of their mod, it is the same as charging a price to download. I remember back in the hideous days of WoW players were offering a premium version if they donated (I am seeing Aether II doing this as well) and Blizzard slammed their mighty hammer down on the modding community and threatened action if they did not stop immediately.
As for the mythical API of Minecraft and the thoughts of a market place. In order to sell your mod (which in itself is an original work derived from another original work) you would need to purchase a permit or get a release from the original developer to sell the mod for a price. Anyways the Minecraft API is a urban myth lol. (look into iPhone apps for EVE Online to see the huge debacle that took place there).
Main reason i hate it is becuase even though its only 5 Seconds, you get 0.05p per Click.... SERIOUSLY.... WHY THE FUCK WOULD YOU BOTHER