I've done this, I emailed around 250 different websites and ended up getting around 30 links. It was a long slog writing the emails as I wanted them to be as personal as possible to get the highest uptake. Interestingly, once the campaign ended I did see some drops on keyword positions so, is it worth the effort, probably.
I'll see if I have the spreadsheet of emails and website URLs still, might be worth a share