Like others have said, I've had some success finding or being found, but job boards are one of many tools and techniques that should be used when looking for work. I look at them as being able to put up a free billboard in every major location.

As for spam, etc, I use a specific email account for work searches that I can activate & deactivate as needed. After I find a new position, I block all messages for a long period. Long enough for bulk recruitment and spam to stop. Then I turn it back on, just in case a real opportunity happens to come in.