Megamergers like AOL-Time Warner and Sprint-Nextel failed primarily because due diligence on big acquisitions, even by public companies, is far less diligent than it should be in terms of evaluating risk and synergies. Then you've got Sony going completely beyond its consumer electronics competency and venturing into the motion picture business, all the while touting synergies that never materialized.
(iStock) More From MoneyWatch
: When Should You Take Social Security? Think Different: Life Lessons from Steve Jobs 7 Totally Unfair Ways to Make More Money The opinions expressed are solely those of the author and do not necessarily reflect the views of Comcast.