Story just says the landlord was contacted by a 'mutual friend', who suggested McGinniss would be a tenant who would 'respect the Palin's privacy'. Sounds like the landlord was concerned for the Palins, and likely is horrified knowing who is actually in the house, now.
That’s what I thought at first. Unfortunately, what really happened is quite different: http://www.freerepublic.com/focus/news/2523978/posts?page=23#23