The real sad thing about this is that if they're asking you to post, it implies that what you post is much more likely to make the top page than it is for regular users, which defeats the whole purpose of this site. Let's hope HN isn't becoming a new kind of Digg...
I suspect that if someone were to do this and the content was crass - which it presumably is or they'd post it themselves - it would disappear.
Regardless, I think this behaviour should be actively discouraged by naming the parties involved as encouragement for them to either join the community in an honest fashion or alternatively to try their luck elsewhere.
Assess it for what it's worth. If it's postable, do it. If not, tell them why. That's the polite thing, but you'd be giving free advice, and this approach would hinder your time if it happened a lot.
The company has obviously seen you post a lot to HN. Do they think you're a sucker?
-edit: and if you do, what do you get out of it? You could ask for a favour in return, or tell them to post it themselves and you might just upvote it.
You missed the "post a poll to divert anyone from thinking I'd taking a 'marketing fee' and then push for the best possible rate knowing that people will consider the link to be all the more clean because of my bolstered reputation" option
