First, you're exactly right when it comes to the ability of a company like ours being able to remove bad reviews. We simply CAN'T. Also, we are not in the business of fake reviews either. What we can, and will do, is look through your reviews and ask for those that we believe don't follow the rules of the road for the review site, or those that are plainly from a competitor trying to nail you and push people his way--even promoting their stores in the review of you---we get these flagged for removal. However it is still up the review site whether they are removed or not.
Some other companies that claim to offer a service like ours break the rules by taking reviews from other places and copying them into all of the review sites. This is not "legal" according to most review sites and we won't operate under these practices.
What we do, and recommend anyone else does, is we educate and provide an incentive to our staff to push customers---all of them, not only happy ones---to the review sites. We make it easy for the customers to get there. We have custom built desktop and mobile sites that provide links to all of the major review sites (Yelp, Google, UrbanSpoon, TripAdvisor, etc). For the mobile sites we have collateral all over your store with QR codes on it to direct your customer to the site to choose their review site. On these sites, we also have coupons for you to entice your customer to visit again. We don't require them to place a review to get the coupon---we think that is a little shady.
We also go to all of these review sites for you and not only claim them for you, but we clean them up. We provide a number of services in working on your presence on the review sites to raise your search engine rankings and more. Of course we provide monthly reporting on all of this for you as you should get from any service like ours.
One of our bigger clients, Jersey Mike's, in some of the stores that have followed our every suggestion in how their staff handles things, have seen an increase of over 200% in the number of reviews they get monthly, and their review ranking has gone from an average of less than 4 stars to over 4.5 stars.
Berkeley did a recent study to show that an increase in star ranking of just a half a star on a review site, has provided that restaurant an increase in their business during peak times of around 50%. It shows that people are making choices of where they dine based on reviews for sure.
I'm sorry if this sounds like I am only speaking about how we handle things with my company, but it's the only frame of reference I can speak from---my own. What I can say is that if you are promised by someone that they can remove reviews---that's a lie. Frankly, if the bad reviews are honest, I think you should want to get them---they will help you learn, improve, and grow. Also, sometimes in how you handle or respond to a bad review, you will be viewed in that light by customers looking at you. A solid, customer centered, helpful reply to a bad review is often better than a great review. It makes people want to give the "good guy" a chance to prove himself, if that makes sense.
Hope this helped some.