eBay-Skype ($2.6B, 2005)

The eBay-Skype acquisition stands as a case study in misguided synergy, costing $2.6 billion in 2005 for a voice-calling service that added minimal value to online auctions. By 2009, eBay wrote off $900 million of the purchase price, acknowledging the integration failure. This loss surpasses that of #2 AOL-Time Warner in terms of percentage write-down relative to deal size, as eBay eventually sold a 65% stake for $2 billion in 2009, valuing Skype at only $3.1 billion—$500 million less than the cost of acquiring it. The total realized loss, including the write-off and subsequent sale, reached $1.4 billion, making it 30% more costly than the typical failed tech acquisition in terms of value destruction.