I think almost anyone is a natural born promoter weather they know it or not. When it comes to trying a new product and reviewing it most people IMO tend to give rave reviews, simply because they have tried something that many others have
not AND a lot of guys want to be the first one to start the next flavor of the month or trend in detailing.
This happens all the time, think about restaurants, movies, books... people who eat at a new restaurant on opening day and simply "like" their food and service, go on to tell their friends about how this "great new place" opened up and "you have to try it" when in fact that restaurant simply was decent, but probably no better than anywhere else in town they are used to eating at. Excitement and exaggeration are generated through ego sometimes rather than facts.
I dont think when it comes to detailing that its spamming because spamming is simply chaotic plugging without even the attempt of reasoning and its easily called out. Sure some guys spam but the majority dont try to be malicious about it, I hope
Another big issue, and I even wrote a thread on product reviews and my opinions on them is that people tend to favor things they just spent money on! New $200 wax? Sure its the best wax ever! (how can it not be, you just dropped a pay check on it:huh
When someone is doing a product review with their brand new expensive wax, after they apply it and buff it off they look at the car and again (many guys) will subconsciously think the car looks and feels better with this particular wax on it and then give a review on the forums reflecting those same perceptions. People do this because they want to justify their expense and a lot of times again they arent lying about it they simply cannot control their subconscious.
I have learned to look at products from a purely objective standpoint now and I'll tell you it makes me find and use the best products based on PERFORMANCE rather than prestige or price. Come to think of it I have never purchased a wax or sealant that costs more than $35... ever.