Nokia

Peak Valuation: $35.70 billion

Current Valuation: $33.50 billion

Flagship products: Nokia N90, Nokia 1100, Nokia Lumia 1020

What went wrong:

Nokia slowly gathered rust while trying to make feeble attempts to get back at their rivals and unsurprisingly, failed at it. Turning a blind eye to internal problems did not end well for them. Poor management, office politics and ignorance towards the fact that Symbian is hardly an efficient OS against iOS and Android were their major flaws. 

Kodak

Peak Valuation: $30 billion

Current Valuation: $103 million

Flagship products: Kodak EasyShare

What went wrong:

 Kodak's fall is probably the best example of how an once-raging tech giant who dominated the industry can lose at its own game by being oblivious to change. Digital photography was invented by Kodak in the first place, yet they failed to see the potential profit they would gain by ditching analog. Switching to digital seemed like a waste of effort and money since their sales were sky high by selling analog cameras and films. Turns out, it's better to anticipate the future even if the present seems smooth.

BlackBerry

Peak Valuation: US $55 billion

Current Valuation: US $3.208 billion

Flagship products: BlackBerry Q10, BlackBerry Z10

What went wrong:

Blackberrys were exclusive, premium devices when they first came out. Sadly, they forgot to keep up with the flow of changing tech trends. Lack of apps, high-end hardware that can stand side-by-side with competitors and a failure to deliver previously announced features and products brought them down as Apple and Google started dominating the industry.

Yahoo

Peak Valuation: over $125 billion

Current Valuation: $40.87 billion

Flagship products: Yahoo Mail, Yahoo Search

What went wrong:

Yahoo's acquisition by Verizon wasn't exactly a big hit. This tech giant might have been one of the hottest names when the dot-com bubble started but it quickly lost focus and lacked a proper vision regarding their position in the market. A subpar search engine, mail service and a number of random acquisitions which either shut down or saw dead ends, took Yahoo down.

AOL

Peak Valuation: $222 billion

Current Valuation: $3.9 billion

Flagship products: AIM, AOL Search

What went wrong:

AOL could have written a book called "How to do everything wrong and come crashing down 101" and taken up a spot on a bestseller list just by creating a roadmap of their journey. It started off as an internet service  provider and somewhere in between backdated services and inefficient new products, it got lost. From trying clone Yahoo to an absurd acquisition of Bebo and weak rebranding efforts, it has been a disaster from multiple directions.