The consumer is harmed by all the services and goods that never appear; because it's clear newcomers who looked like competition would be crushed if they tried, or were acquired instead, early. All the dogs that never barked.

I believe it does, but the commenter said size should be the determining factor. I disagreed with that area, but harm to consumer should absolutely be regulated by anti-trust

It's hard to determine consumer harm. For example Walmart is often considered as beneficial to the consumer because of price but you could also argue that harm is done by limiting choice and innovation.