Generally speaking, businesses get a boost in revenue when they have good reviews. Some businesses provide an incentive to their clientèle for leaving a review. For instance, the customer might receive a small discount on next months bill. This isn't the same as paying a professional reviewer who isn't a client to leave a positive review on consumer sites. Do you think incentivized reviews help the bottom line?
Some customers will not purchase a product or service if they can't find reviews about it. This is especially true for items that are bought online. So, I can understand why some choose to incentivize reviews. I don't have a problem with it so long as the company provides the same reward, whether the review is positive or negative.
I think that any reviews help, except for the fake ones of course. Incentive reviews are smart in my opinion, because it makes people more likely to leave a review, something that most people don't do without motivation.
Reviews help, especially when they are written in a sincere manner. Giving incentives wouldn't be a bad idea though I'd be very careful for those reviews that would look 'fake' in the eyes of potential consumers.