I recently implemented many SEO techniques for a company on their asp.net website; in 6 months, we jumped from a PR1 to a PR3. But I'm having issues with google backlinking.

Here are some of the things I've done:

1. Not only did I set up their own Google+ page 6 months ago, I update it pretty much daily with links, pictures, etc., and I blog about it on my own personal Google+ page and post links, etc. ...
2. They have their own Twitter, Facebook, YouTube, and all are updated almost daily.
3. I've listed in as many quality, relevant directories as possible 6 months ago; I've avoided link farms.
4. The site is solid SEO-wise. Key-phrase rich URLs, schema.org & rich snippets.
5. No duplicate content ... www or non-www 301's, trailing slashes, etc. ... all taken care of.
6. Probably a ton of other things, but basically, the site is all set, SEO-wise.

Here's what's confounding:

When I do a link:www.example.com in Bing/Yahoo, it shows many backlinks. When I do a link:www.example.com in google, it shows up 0 links. Or when I use a site-ranker like Web Site Rank Tool it's showing 0 backlinks from Google. Any suggestions would be appreciated!