How odd. 
Never known anyone do this. I have never done it, and no-one I know does... I agree with a few posters @Sophieagain1984 that just because they seem nice when you first meet them, that tells you fuck all. I have known LOADS of occasions where someone seems 'lovely,' and when you get to know them better, (and sometimes when they've been on the booze,) they turn into arseholes... Who play very loud music, up the volume of their voice (X 5!) have 3 or 4 yappy or barky or aggressive dogs, and have loads of people around, making lots of noise, and making it hard to get into your driveway (or find somewhere to park if you don't have a driveway.)
I have had people knock my door though (when next door was for sale,) and ask me if the neighbourhood was OK (- well I wouldn't be living here if it wasn't! -) Around 8 or 9 people knocked, before I stopped answering!
A few people of these 8 or 9 asked me if the house had any issues or problems they should know about! About 4 people asked me that! Pissed me right off that did, especially as I knew it needed a new roof, new soffits and guttering, and the entire wall along the small back bedroom on the end - (inside and out,) and the dining room wall (also inside and out) were both riddled with damp, (but I knew it was not my place to say anything.)
Put me in an awkward position. I just stopped answering the bloody door when people came to view! With the ones who did catch me, I just said 'I have no idea.' It was fuck all to do with me! I wasn't gonna comment.
It had been a private let for 10 years and like most landlords, the owner who rented it out didn't give a shit about it. Took 2 years to sell, and fell though SIX times when the prospective buyers had it surveyed. It eventually went to a lovely couple who knew of all the issues and knocked the landlord down by 15%! They spent a year sorting it and now it's lovely.