The medium via which information is presented is an integral component of any contract. For example, if a content provider provides you with content without a fee, then it probably has a revenue model that involves some secondary effect of you viewing the content, e.g. advertisement viewing. If you bypass their system and extract the information you want directly, in a way that violates your contract, then you are depriving them of their revenue. No matter how you slice it, taking something without authorization from someone is stealing. Furthermore, via your automation you may be harming them via resource over-taxing. There are very good reasons for prohibiting "robots" from accessing web sites, and your selfish disregard for them invites a Tragedy of the Commons.

There is plenty of precedent for content/service providers going after people who violate the terms of their service agreement. Don't take my word for it though... Just ask some of the people who have been taken to court by eBay.