The current scrutiny of anti-competitive business tactics by Amazon.com Inc. by both U.S. and European Commission regulators has put its pending acquisition of Roomba maker iRobot at risk, but there are hopes that tech M&A will come back this year nonetheless.This week, Amazon AMZN, +0.94% missed a deadline to file concessions to the EU that would allay any concerns the regulators have about its pending $1.4 billion acquisition of iRobot Corp. IRBT, +4.37%. IRobot makes the popular Roomba robotic vacuum cle ...