A person who quickly buys into and acts on media or marketing hype.
HM1: Did you hear about the new $600 4G phone? It totally puts my $550 3G phone to shame.
HM2: I heard it gets 5% faster download rates and has copy-paste now!
HM1: Let's throw out our old phones and buy these new ones!
Casual Observer: What a couple of hype monkeys.