That's because I haven't developed or promoted it, and only a few people have thought of the term independently of me. I'm sure "shopzilla" wouldn't have returned many results in Google pre-2001 either. I think "reviewtopia" is just as descriptive, catchy and pronouncable as "shopzilla," and a good deal more clever (the last syllable of "review" becomes the first syllable of "utopia"). I was actually surprised that no comparison shopping or review aggregation upstart had thought of it before me. I think it would make a great brand.
What if I created a mini-site and pumped it up all over the internet so Google turned up lots of hits? I guess the domain would be more valuable then?