Newbie - FAQ
To answer your questions...
All of the above, and then some...
What I mean is, yes, there are times when providers have attempted to prop up their scores by posting false reviews. TER is pretty good at spotting this (not 100%, but they try). When they believe a provider has posted a false review, she is de-listed and banned from the site. It does happen though, in spite of their best efforts. Providers can also attempt to manipulate their reviews by offering discounts in exchange for reviews (Many a thread has been dedicated to the ethics of such behavior, the jury is still out on whether it is ethical, and I am not mentioning this practice now to start yet another debate 
On the flip side, you asked do hobbyists submit bad reviews to be spiteful? Sure, you bet. Are there reviews where it was the hobbyist who was the dissapointing one? Certainly. This is why the phrase YMMV (your mileage may vary) is important. No matter how wonderful a lady may be, there is no such thing as a woman who can be all things to all men, so it is inevitable that at some point, she will encounter a gentleman for whom she was simply not his cup of tea.
Also recognize that providers are humans too. Sometimes a woman just has an off day, and simply isn't at her very best. I am certain that if you were evaluated in your profession on a daily basis, there would be days when you are outstanding, and other days when your work was only so-so.
The message is, take reviews with a grain of salt. They serve a very useful purpose, but they aren't necessarily the gospel either. Take them for what they are worth - a useful guide, but not a silver bullet. If a lady's review history has a few blemishes, but is overall consistently positive, and she appeals to you, then proceed with caution if that is what you want to do.
