Google do not show all the backlinks if you do google link:www.yourdomain.com,try http://www.google.com/webmasters tool to view all of your backlinks.
Also, Yahoo! does not show all true backlinks. Many are usually internal links to your website, links that are using the nofollow attribute or links that really have no SEO value due to their redirection method.
As mentioned, Google hides a lot to the public. Check your Google Webmasters account for an accurate view of your links
This is normal as google usually hides the majority of your backlinks and yahoo shows many links which are discarded by google.
When you do link: www.yourdomain.com, Google will show you only the important backlinks. From my experience, in Google Webmaster Tool the backlinks not appear fast, is need to pass some time
I have 10,000+ back links in yahoo, but only 4000 in google. Its normal. I guess google only show back links which google thinks are important ?
well, in this case you should go to yahoo and type in the search box this: linkdomain:www.yourdomain.com -site:www.yourdomain.com The results will not show internal links!
Google updates inbound external links in a period of time and they emphasize highly on quality. So dont worry if you have 3 backlinks to yahoo's 300. The ratio is fair enough.
What is strange - Google tend to show poor quality back links as well. While relevant high-quality links are hidden for months... or even longer periods.
this isn't unusual - my forum shows under 100. - had over a 1000 at one point lol - yahoo shows over 30,000 still lol