And I may guess Google is protecting the sites by not letting the competitors know its exact back links
Google knows every things about your good and Bad neighborhood of back links but Google is not showing all the back links, you may check external links in Google webmaster account of your site. and second option is yahoo site explorer that you know very well. Eric
Actually I find Yahoo better at counting backlinks even when taking google webmaster tools into consideration.
I agree with what tradeya said above...different companies have different ways to detect..i also use 3rd party sites to check the backlinks and they too show different results
Yahoo explorer is indeed better to check inbound links. However you can use to check backlinks in Google
for my sites yahoo tracks more backlinks, but google used to track more backlinks than it does now. I have one site for the past 3 year that used to have 900+ backlinks, now has only 200+, but yahoo is still reporting something like 700+. It used to be that google would track lots of links many times. If a site translated into a bunch of languages, and used different country domains, then I'd get a backlink for each. There is a lot less of that now.
If you want good back links in Google than check your competitors who is ranking good in google . I am using http://www.backlink-tool.com/ this Google tools and keep post in comments on their links .
Google is very slow listing the backlinks.... if your site is new, you have to wait some time... and yahoo is very fast in this job.