Genealogists and family researchers use Google and the other search tools A LOT to find information about their families.
If you have your own blog or website, and can create one webpage with information about the family names and people and places you are researching (not all the info, just the high-level stuff), then that will get indexed by Google and the other search tools.
When people search for a certain rare family name, or a more common family name in combination with a given name or a place, your page will then show up on the various search tools and they will contact you.
This has worked very successfully for me. I get about 20 contacts a year from my site and several each year turn out to be relatives I hadn't communicated with before. In all cases, they are very interested in collaborating.