Similar concerns were raised a couple of years ago when Yahoo thought (foolishly) that it would be a good idea to "recycle" email addresses:
http://www.cnn.com/2013/06/20/tech/web/yahoo-recycled-email/
http://www.cnn.com/2013/06/20/tech/web/yahoo-recycled-email/
I had an account expire ~10 years ago. Somebody else registered the address and used it for several years, then eventually let it expire as well. Last year, I re-registered it, and used it to recover access to an account I created a long long time ago.