Dell's $67 billion purchase of EMC is the biggest pure tech acquisition ever. (AOL's $162 billion buy of Time Warner in 2000 was larger, but Time Warner was a media company, not a tech company.) This chart from Statista shows some of the largest tech acquisitions of the past decade, measured in 2015 dollars.

There are a lot of dogs on the list.

HP's deal with Compaq didn't lead to the expected synergies and was part of the reason the board fired then-CEO Carly Fiorina. HP is now laying off thousands of people from the Enterprise Services division it created largely out of its EDS buy, and it's involved in litigation with former Autonomy execs after writing off $8.8 billion in value from that acquisition.

Google only held on to Motorola for 2 years before spinning most of the company back out to Lenovo for less than $3 billion. Microsoft-Skype and Oracle-Sun were neutral at best — neither one helped the buying company create significant new businesses, although some of the technology and expertise might have percolated through the organizations.

Of all these, only Facebook-WhatsApp falls into the "too early to tell" category.