Great sales people are a game changer. People that can sell your vision and convince the audience that the problem you're solving is the biggest issue their business faces. They're completely indispensable. Bad sales guys, the type I've usually come across, bring too little domain and product knowledge to the table, and end up selling the completely wrong thing if they sell at all. Like Ben Horowitz said, great sales people protect your business , they don't wreak unnecessary havoc on it.
This is where a huge amount of the rub between sales-marketing and dev comes in. But this "imagine all the possibilities" type of stuff is pure crack in the sales-customer relationship.
So I try to fill the void for the sales guys so they won't be making stuff up on their own. That is, I take a lot of care/explaining to them what are some of the near term possibilities of our app that we haven't built out yet, but make sense, that sort of thing, how much it would cost, risk factors, etc.
Fill up their fantastical story buffer in advance w/stuff that is acceptable to me. This seems to work well with little friction because sales guys tend to be a lot less intransigent than devs/designers about features - basically, they care less about the substance of the story rather than simply how well it sells.
In short, I try to make my fantasies their fantasies as well.
Simple example: there are a number of guns that can be converted from semi-automatic to full-automatic with very simple changes, removing a spring, filing something down, etc. If you've got a pack of wolves coming at you the rate of fire could certainly change the balance in your favor.
It seems like we are getting into further trouble here. As this pack of wolves is stampeding (never heard of wolves stampeding, though) at you, removing the spring, filing something down might not be consistent with the very short period of time you have as this herd (?) of wolves is closing the gap on your, er, person.