Buying LinkedIn means Microsoft will control the best-known network.
Tech companies typically do lots of business overseas and book profits in low-tax jurisdictions.
Fears of Chinese economic troubles and slowing iPhone demand vaporized more than $100 billion of the company's value since mid-July, reducing its market capitalization to $630 billion.
The $9.5 billion Nokia deal was the last in a string of bad deals struck by Chief Executive Satya Nadella's predecessor, Steve Ballmer.
Shareholders may once again be underestimating the staying power of the company's margins.