It's just too easy to make fun of people who know nothing about bicycles. Cervelo and other similar companies are successful only because so many newbies buy their overpriced bikes. They want to be the fastest guy out there, because riding for them is passing dudes and not being passed. So they buy the bike that has the fastest image. It might be a Cervelo, or it might be any of the other popular names in that market segment.
For many, it's the first and only serious road bike they have ever had. Riding it compared to a hybrid, comfort or mountain bike is a revelation for them, and then they assume it's because of the Cervelo name on the downtube (or substitute Madone, Tarmac, etc.). Then there's the natural tendency to defend to internet death one's own current purchase, no matter what rationalizations have to be employed. Put all that together and you get the basis of 80% of bicycle forums posts on the internet.