This is a little tip for you hardy folk who still have the patience to do BLB.
So, you send out 100 emails and one webmaster responds favourably. Instead of removing the dead links, volunteer to find alternative sources.
As you help him fix the broken links, create an Excel spreadsheet. Three columns per tab. Record the broken url, the alternative one and the resource url (the page you're fixing).
Now, after the changes have gone live, go through the "alternative" column and collect the webmasters' contact details. Get in touch with them and tell them that
"I recently helped a pal to fix a website and I've updated his resources page. I selected your page for //insert resource page url// because //insert why you think his page is amazing//. Please let me know when you add similar content in the future...
or something like that. Also don't forget to follow them on Twitter.
If they respond (and in many cases they will), all you have to do now is pitch for a guest post or show them the extremely cool linkable asset you've built.
Also (and this will be obvious for many but I will still mention it) don't forget to go through the "broken" column and check the urls via MajesticSEO or whatever you're using for link research.
Chances are that if the initial target linked to that broken link, there will be other webmasters linking to the same page.
So, just one initial broken link has suddenly exploded into many opportunities. Yey!
I do supply an alternative url where the site still exists but the page linked to doesn't, but I haven't suggested alternative sites altogether to now because the less links there are on their page the more mine might be worth :)
One thing I've started doing is to reformat/regroup the raw Xenu information by error type - so all the 404s together, all the non-existent domains together etc. Takes longer but makes it more friendly.
I also explain how I got the information and link to the Xenu download.
I also don't send the information as an attachment, in case people think it's a virus - "Hey, I blah blah blah, why don't you open this attachment to see what I'm on about?"
I also ask for the link from the outset but keep the discussion on abstract reasons such as 'looking to raise the exposure of my site'... 'a mention on an authoritative site like yours would really help' etc - nothing technical.