Rating systems of eBay and Amazon

Many online merchants today, such as eBay and Amazon, use rating systems empowered by its customers. Is this adequate for determining which products to buy, or which users to trust? Cite examples from these two merchants that support your opinion (whether it is good enough, or inadequate).

I think using a rating system for websites such as eBay and Amazon to aid customers is effect in the sense that it narrows down options for many people and provides some basis of accountability. For example, on eBay there is a Gucci watch selling for $225.00. The seller of the watch is labeled a "Top-rated seller" and has many comments about how well the transaction went when customers have bought their items. As people see the hundreds of comments, the green checks, and the "top-rated seller" badge, they are more comfortable doing business with this seller. When you're spending a lot of money like this buyer would be, you want to make sure you're not getting used. Ratings such as A+ and top seller allow buyers to trust the seller more.
On Amazon (amazon.com), a Canon PowerShot camera is being sold for $199.00. The camera has 4.5 (out of 5) stars and 233 customer reviews. The customer reviews allow for the buyer to actually read personal opinions about the product instead of just seeing a rated number. Customers wrote out information and I think this really helps potential buyers to feel comfortable with what they're getting. Since buying online can be ambigious, ratings like these and customer reviews really help to make it easier. People want to give their opinion if a product is good or bad. I think that makes these reviews reliable and helps customers decide on what is worth their money.