Yeah, this is a pretty standard answer to the same market failures that so many people have been talking about recently. It assumes though that low prices are the best possible benefit consumers might get from competition, and it also assumes that megacorps necessarily lead to the lowest possible prices for consumers.
Chokepoint Capitalism is a pretty okay book that kicks the legs out from under both assumptions.
I don't think I'm making any assumptions about what's best. I bring it up because the most common argent levied against mega corps is using monopoly power to drive up prices, which I don't think is always true.
If people specifically want to break them up to drive down prices, I don't think that will always be successful.
The problem in my mind is that the largest companies have too much efficiencies of scale to compete with on price.
When competition can't undercut on price, it is hard to argue that customers aren't being served by monopoly mega corps.