I'd be careful with that. Most people probably wouldn't try too hard to promote you, and "just tweeting so I can use this crappy inbox cleaner. bit.ly/asdf..." isn't really great promotion.

In general forcing viral activity both misses the point and fails to work. I'd say you should at most randomly give away free inbox cleanings to your followers / people who tweet about the service. Really, though, you should probably just be active on twitter and talk to people. That doesn't scale well, but it's the most effective viral tactic there is.

I've done it once. And it worked. You just need to be upfront about it. Most people don't mind a plug in exchange for something free. And the ones that get snarky about it (a tiny minority) are not a big deal. The ones that really care will pay you (an even tinier minority).

This works because you're offering something that normally costs money for free. That's psychologically different than offering something for free (with a required plug), but with no option to pay for it.

The other thing is that it needs to be an impulse purchase. I doubt it would work for a Shoppify, for example.

So if you're selling something sort of whimsical, entertaining or trivial, this sort of "forced viral" marketing can work very well.

with oauth access you can push the tweet yourself. Of course, tell them what they will be posting, but you can control the message.

In some ways that seems even worse. Canned messages that you have to inflict on your friends to use something are one step shy of pure spam. They also seem to be ignored in much the same ways.