There are channels where I am open for contact and channels were I am not open for contact. I notice many recruiters email my github contact address to ask about stuff on my linkedin for example. I'm not sure if they've personally scraped my commits or just bought a database of "developers in Europe" to link the two together. They could use LinkedIn, or the contact email I put on my CV (including the public copy on my website, which is linked from linkedin, and then it gets categorised appropriately. But it just seems kind of cheeky to route around that, like cold sales calls.