The Inside AdWords blog has provided more information about how landing pages will negatively impact your Quality Score. They have now provided a FAQ that answers many of the landing page questions as they relate to the Quality Score.
A few landing page types that are frowned upon: data collection sites that offer freebies in order to collect private information, arbitrage sites, and sites that install malware on visitors' computers.
Forum reaction is pretty much summed up by this: "Thanks, Google." Even though it should have been obvious before, it's nice that Google is finally making it a policy.
A few people, however, are worried that they'll be negatively impacted. For example, one user requires personal information for freebies which is one of the new restrictions.
What about honest newsletters? One of my sites is a weekly newsletter about a certain craft. I advertise it as a newsletter and the only thing on the landing page is the description of the newsletter and the signup box.
The question, then, is how much information does the landing page need to ask for in order for it to break Google's guidelines?