Two weeks ago, Barry at Search Engine Roundtable noted that when you check for the number of links at Yahoo! Search Explorer, there is a discrepancy between the values shown between logging in and not logging in.
Priyank Garg from Yahoo! Search has replied with positive developments regarding this issue. A product fix has been done yesterday and soon we shall see the same number of back links (in links) and indexed pages whether we login or not.
This is more helpful than Google’s Webmaster Tools that doesn’t show the accurate numbers if we don’t login. Google has a point though: you login and you get more accurate information. Don’t login and you won’t. Google is more unwilling to share a web site’s information to unverified owners or folks who want to eavesdrop over competitor performance.