I've developed a well received niche information site over the past 24 months, having spent several thousand man hours at it. The site has a PR of 5, ~ 500 inbound links (many highly authoritative, many .gov and .edu). Google and Bing have received us very well, but Yahoo seems to think we're nothing. HELP... What might be some credible reasons we're not getting indexed well? (We do have 3-4 pages linked it seems). I even spent the $299 for the Yahoo Directory early on, but that seems to have been wasted money.

Any tips or information would be greatly appreciated.

It used to be that backlinking the heck out of it used to help websites in Yahoo. But I believe their Algorithm has changed to reflect Google's. You can't merely backlink to rise up in the SERPs.

Honestly I wouldn't lose a lot of sleep over it. If you're doing well in Google, that is literally 70% of the battle... Yahoo! and Bing are fighting over the remaining scraps.

One day (Maybe!) Bing will start providing search results for Yahoo! at which point, the Yahoo! algorithm is a mute point.