It's pretty high. I normally completely ignore generic recruiting e-mails that have made no effort to find out more about me. If someone's gone to the effort of

It's pretty high. I normally completely ignore generic recruiting e-mails that have made no effort to find out more about me. If someone's gone to the effort of looking into my work in detail I'll normally repay the kindness by replying. Case in point, a few months ago Udacity sent me an e-mail which went in some detail about a blog post I'd written, some of my Stack Overflow answers...it was pretty clear the person writing had actually taken the time to read some of my stuff, so even though I wasn't looking at the time I wrote back to thank them. As other people have pointed out, this also works the other way round. I actually 'reverse cold-recruited' an interview out of Stripe a year ago using the same methods, just applied from the perspective of the job hunter rather than the recruiter.