The main issue for readers is privacy. Because you are searching and reading on a public network, there is little assurance that your browsing and reading habits are private. Here are some of the questions raised by groups such as the Electronic Frontier Foundation:
Are your reading habits safe from fishing expeditions by the government or lawyers in civil cases?
How will Google itself use information about your reading history?
How will Google combine information about your reading habits with other information it may have about you through its other products?