I think you are overlooking a flaw in properazzi's model. I may be biased, so I'd be happy to hear why I'm wrong. But here's what I think:
A real estate agent's listings will change day to day, as some are sold/rented and other new ones come on to the market.
But properazzi scrapes agents' sites. Even Google can take a couple of weeks to reindex a site. Even in Properazzi took half the time as Google, it would be too long for property hunters.
As a home hunter, do you want to see last week's listings while other home hunters have the advantage of seeing the latest ones. Which of you will get the best place?