According to discussions at WebmasterWorld and elsewhere it appears that the Yahoo! Keyword Suggestion tool has frequently been unavailable and causing errors with software that rely on its data. Speculation is that it may not be much longer for the world.
How sad. I've been using the Keyword Suggestion tool since it was first online and haven't had any problems connecting of late. It has however been SLOW as molasses for a long time.
Although Wordtracker estimates search volume differently than Yahoo!, the data seems reasonably comparable.
For example, I searched for the term ‘personals' at Overture, which reported 288,953 searches for the term in December 2006. I then searched the same term at Wordtracker which estimated 10,044 daily searches. Dividing 288,953 by 31 days in December gives you 9,321 searches per day — a difference of 723 searches.
Good enough for government work – is it good enough for you? 🙂