censormuch, I think you're missing a key point. No where does CurbTXT say they promote, excuse or "condone" illegal parking practices. It's simply a communication tool for notifying car owners of ANY issues with their vehicle. You can of course always tow if someone blocks your driveway. By using CurbTXT, you are not granted any immunity from parking violations, but you are allowing people to contact you directly. It is simply giving them a choice in how they make contact. If you are abusing the use of CurbTXT by say perpetually or indiscriminately parking wherever you want, you most likely will be towed, CurbTXT sticker or not.
However, if you happen to have left your lights on, or forgot to rotate your tires when on a hill, any neighbor can help you out with a friendly reminder. Other benefits would allow people to contact you if they noticed your car was being vandalized (by say someone keying your car).
Of course, CurbTXT isn't for everyone. And it doesn't look like it's offered outside of the States anyway, so fret not, you won't need to worry about helping or being helped by neighbors anytime soon.