Firstly, note that I did not do any research looking for information as to why the listings that I've seen have mostly been out of date. By out of date I mean that when I ask an agent friend about a house I see she often tells me that it is already sold, sometime MONTHS in the past. That said, read on...
My experience with Google maps mls listings is that they are hit or miss as to whether or not the listings are really on the market. I suspect (warning: paranoid theory) RE agents don't want Google's data to be too accurate. This is one way to try and maintain relevance as technology rapidly changes underneath them. I think this, if its true, will ultimately hurt the RE industry. It could be that agents just don't remove things very quickly from mls - that coupled with any delay that Google has syncing up couild account for the perceived inaccuracy.
I think that as more and more tech savvy buyers and sellers enter the market they are going to expect accurate data - wherever they get it. They are going to be annoyed by inaccurate data, and enter into RE agent relationships grudgingly. Better, for RE agents, to focus and adding value to the data - good services added to the data is always valuable. If you know your town and are willing to get to know the customers and are then able to show them units they'll really like long term, you'll do well.
I wonder what your trade organizations have to say on this... Also, look to the RIAA for a bad example. They dragged their feet and ceded the market for digital music to Apple.
If you're a RE professional, I'd be happy to talk more one-on-one... My fee is usually satisfied with lunch ;)