Yahoo's Slow death began when they lost their yahoo messenger base, Search people already started using google back then and when there is no need of messenger many people forgot about Yahoo's Existence.

I used to mail/search/chat/read on Yahoo frequently 8-10 years ago, it became occasionally 4-5 years ago and Rarely since past 2 years.
Thats the degradation.

I loved and Love Yahoo for the products and Innovation they brought but unfortunately they are Just Bunch of Innovators out there.

I have been inside yahoo premises many times, and what I found is lack of vision in terms of business acumen. That lead to many lost opportunities.

I Strongly feel Google in Search is unbeatable, But Google is following Yahoo faster towards brainless products.