You are right Phizzy it appears that this caution was eliterated about 9 years ago. I did a quick search and there was a thread about. I think what struck me this time around is the tone the letter had. It was a" pointing the finger" type of letter no doubt carefully crafted by their lawyers. The sense was that "if you disregard any of these signs, we wont back you up and you may be sued----so there".
I remember the sleuty ways we would get in apartment building as Rebel 8 mentioned. My poineer partner and I would wait around until someone would enter, then sneek in and start from the top floor. We would do a few doors and then go the the next floor . Eventually we would find some irate person that would call security and we would be kicked out. But then we would do it all again the next time.
When I think about it now, I am so ashamed of some of the tactics that were used to infringe on others right to privacy.