Microsoft invested in Apple in 1997. The DOJ filed suit in 1998.

It was a tactic to deflect a DOJ suit, unsuccessfully, but again, this was likely not an appropriate use of the government’s authority. For the sake of argument, even if it were, that does not mean it would be today. Present circumstances are not a mirror of the past. If you want to make a good case for government intervention in the market, your best argument is not that the United States once sued Microsoft and now it is Apple’s turn.

Mind the DOJ has sued Apple (and publishers) once using antitrust law relating to the iBooks Store. The result further cemented Amazon’s market dominance in ebooks and increased ebook prices.