1. Microsoft has a long-held belief that people should have choice and control in how their personal information is used on the internet. You can read more here.
2. From the official blog post: One potential downside is that some web site publishers and developers already have concerns with large numbers of visitors blocking some of the content today (usually ads). We understand this concern and have provided several ways to deal with this issue. First, this functionality is opt-in, and by default consumers’ experience will remain the same as it is today, unless they make a decision to change it. Second, any site can make available a Tracking Protection List that creates exceptions (via “OK to Call” items) for external content that provides the full experience of the site. This TPL provides transparency to the consumer about the additional sites he will visit and share information with. Third, a site can pull external content into its own domain, so that a consumer has no need to call external sites. Lastly, networks of sites and associations can work together to create a TPL that they recommend broadly to consumers. We designed the feature so that there are ample opportunities for all the constiuencies to engage in a manner consistent with their priorities and point of view.