This is classic behavior for bull markets.

 

This is classic behavior for bull markets. You can see the revisions trend rising as the price of the S&P500 keeps heading higher:

As investors we all have that herding mentality. It's perfectly natural. We've thrived as a species for many reasons, but one of them certainly being our ability to stick together and work together. Our ancestors used this to fight off neighboring tribes or wild animals. But we don't have those problems these days. Our brains, however, are hard-wired to think this way.