I get mostly relevant opportunities, but they never acknowledge that I'm already running my own company, even when contacting me via LinkedIn where that's prett

I get mostly relevant opportunities, but they never acknowledge that I'm already running my own company, even when contacting me via LinkedIn where that's pretty obvious. These aren't exactly no-name companies or recruiting firms but the actual companies themselves - we're talking about Zynga, Playdom, ngmoco, etc. Is this something other founders have found?