I'm not going to put a [status-*] tag on this yet because we don't have concrete plans with a concrete ship date, but as a product manager thinking about how to improve the experience of job seekers on Stack Overflow, I did want to let you know that we're currently thinking about how we can better match candidates with jobs we're confident they'll like.
We're considering a lot of different variables that feed into how good of a match there is between companies and developers, but one of them is definitely salary. A few months ago, we started collecting (but not requiring) salary information from customers who post job listings on the Stack Overflow Careers job board, and displaying that information to candidates viewing the listing. A natural corollary to that would be asking candidates what their minimum required salary is.
I'm not sure whether we'd want to directly expose that number to companies, but I do think we can use salary as one (probably heavily-weighted) criterion for a relevance sort on the company side. So when a company is searching for candidates in our database, the candidates at the top of the search results would be ones who have specified a minimum salary that is within the range offered by the company. We would still show them profiles for candidates whose minimum salary was above the range the company offers, but they'd be much further down the list.
Ideally, the end goal is to have us (Stack Overflow) be good at recommending developers to companies and jobs to developers, but to get out of the way and let everyone make their own decisions. If we can say "hey, this looks like a good match for you and it's because you both want X, Y, and Z", we can let each side determine whether X, Y, and Z are enough, or if they are going to pass on this person / job because they're really looking for A, B, and C, too.
As I said up front, we don't have a specific feature planned right now, but we do plan to incorporate salary into a better system of recommending which developers a particular company should consider reaching out to. We probably won't prohibit contact between companies and developers whose salary ranges don't match, though, because some companies might be able to negotiate, and some developers might be okay reducing their salary a little if other benefits add to the total compensation (like if the company pays for 100% of the health insurance costs or something – not salary, but for many people, this benefit would increase the amount of money they actually get to keep from their paychecks).