Phone jacks anyone?

On and off over the past 3+ years I've noticed a few handmade posters scattered around my neighborhood with large block letters that say "Phone Jacks" followed by a phone number. I always thought it was odd - who needs phone jacks? - and that it must be a front for something deviant, but never called. Finally, after seeing another one the other day I did a Google search and found this article by a blogger who shares my suspicions (but worded them more eloquently.) My boyfriend Googled the number last night and said that the listing gave a strange name and a zip code. We're working up the nerve to call. None of my friends have noticed the posters and I haven't dug up any additional articles or posts about it, but perhaps someone will see them and come across this page with their own theories!