I doubt you'll get anyone who says that salary range disclosed in a job advertisement is not a good thing, from the perspective of the job seeker.
The question you may want to ask instead is: "Does the benefit to the job seeker of having a salary range specified outweigh the loss of potential advertisers who do not want to disclose a salary range?"
If you're just doing this as a side project, with no expectation of making a business out of it, then you may want to lean more toward what benefits the user.
If you're trying to run a business and pay the bills, you might need to think more about how it decreases your potential revenue, assuming the job advertisers are the ones who are paying for your service.
One other thing: Salary range is inherently a fuzzy concept. It's possible to set limits (e.g. the range must not span more than $20K, or the range must not constitute more than 20% of the lower-end number) but then you have to take into account that an advertised salary range is not necessarily the same as what they're ultimately willing to offer you. And then you have to factor in benefits, etc., which can make salary ranges misleading.
Edit: One possible way to make salary range disclosures more palatable to advertisers is to borrow a strategy from matchmaking systems: The advertiser discloses a salary range, and the job seeker discloses a minimum required salary, to the website, which does not make any of that information public. When the job seeker submits an application for a job, they receive a notice if the advertiser's specified salary range does not meet their minimum requirements. This keeps the actual salary range out of public view and at least slightly difficult to estimate, but it prevents the job applicant from wasting their time.