Even if so, this is an acceptable incentive for people to comment with Amazon links. If find this a problem for services like http://hackernewsbooks.com/ http:

Even if so, this is an acceptable incentive for people to comment with Amazon links. If find this a problem for services like http://hackernewsbooks.com/ http://hackernewsbooks.com/ (there are few others). If someone mentions just a title of a book, it doesn't get indexed.