We think it's obviously more complicated.

Job Boards are just one tool - like an allen wrench.  An allen wrench (also known as an Allen key, a  hex key or a hex head wrench) is a tool used to drive Allen screws and bolts, which have a hexagonal socket in the head.  It's not the only kind of wrench and certainly not the only kind of tool. Wrenches are hardly the only way to install fastening devices.

One of the most significant flaws in the sort of thinking that produces the fire-hose problem is the idea that there can or should be one kind of tool, one system or approach that fits all circumstances. For a problem set as large as "matching all companies and all employees in the world", the idea that "a one size fits all" approach could possibly work suggests a troubling level of cannabis intake.

The labor market is huge. Local customs and manners, the balance between privacy and economic need, economic conditions, acceptance within an industry, technological infrastructure, local human rights policies (think China and some portions of Africa) and a host of other factors drive job board utilization. The factors that drive job board performance are equally diverse.

When the local economy is bad, job seekers outnumber jobs by definition. Job boards, niche or otherwise, serve to amplify this reality. Response volume is partly a function of who can read the ad. The internet makes it possible for people in a bad economy (say Bangladesh) to see and apply for jobs in a good economy (say Spain).

It's not an inherent flaw of job boards. It's a widely touted benefit of the internet. (That's the famous it's not a bug, it's a feature argument.) It's one of the remaining strengths of the newspapers. (There are are some jobs for which it is vastly smarter to advertise in a newspaper.) When you wish to reach the local market of people who read the newspaper, the newspaper is the best place to reach them.

Desperate tactics (like fanning your resume out to thousands of email addresses) used to be cost-prohibitive when distribution was paper. It's cheap and easy when the cost is nearly zero. In this case, it's not the job boards who cause the problem. Rather, it's the reluctance of companies to fully invest in infrastructure. As long as there are more people than jobs anywhere in the world, an overabundance of candidates will forward their data to your job application.

The nature of markets is to have and fix imbalances. Almost always, the last fix creates the next problem. In this case, the real culprit is the business cycle. When times are tough there are too many unqualified applicants because there is an overabundance. When times are good there are too many under-qualified applicants because there is a shortage.

All the job boards do is amplify the issue.