I do not know about the situation in Munich, but I spent lots of time looking for a place in Bonn last year and from my experience the approach from the article has one serious flaw: While the real estate websites offer contact forms to send e-mails, many people hate dealing with e-mails. Landlords and even "professional" real estate agents often ignore e-mails. Sometimes it is because of the sheer volume they get, b…
I was going at first to agree with you based on my experience with Berlin: when the ads there give a particular date in which the apartment will be shown, those interested have to fill a form right after seeing it. So in this situation there's no incentive for the owner to check the e-mails. However, that doesn't explain why both the Italian girl and Hanz from Munich got over a 90% answer rate - if they didn't check…
But originally he was not out to mine this data. He actually needed a place to live, and I wanted to point out that he might have approached this the wrong way.
Personally I prefer e-mail over phone calls. A lot. So this was not obvious to me up until my experience last year.