Where are those employed? I have never seen it; from small companies to MS (and especially Oracle), from services to product companies. They don't right-out lie because they've actually been drinking the kool-aid so they do not really know that actually the stuff they sell is hard (impossible) to produce. I'm talking software here; no clue :) about other branches of business.
Sales guys are great fabulists for the most part, so in the absence of "blue sky" stuff for reveries w/potential customers, they will just start riffing on their own independently.
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.
I've worked with one or two of those (out of about something like a hundred, I'd guess). Both came from technology and had engineering degres but had figured out they preferred sales. I'm not sure that's the sole reason, but they really did grok how our solutions worked, what benefits they offered and how to map that to the customers desires and idiosyncrasies.
I come from technology, but when I have my sales-hat on, I become full-on sales and when clients ask me questions or when I ask them questions, I read their expressions and hold my own in any way to maximize sales. I find myself sometimes walking out of the clients' office thinking WTF did I just do?