Question regarding Google places

these are some of the observations i have picked up from net regarding Google Places.

1. Google reviews dont play a major role in the rankings

2. These reviews are inaccurate, and they disappear for no reason.

3. it is not advisable to buy them

4. Ideally it is good to ask customers to post/repost reviews, google doesnt mind that

5. This is Interesting: Note to any business owner reading this post: If you cheat, Google WILL FIND OUT. You aren't the first person to attempt to leave fake reviews. Google knows how many pieces of toilet paper you used to wipe your butt...

Now, here is what i want to know:
Google Places aggregates reviews from a lot of different websites such as yelp, tripadvisor, citysearch, etc. what if i search for a comprehensive list of the websites that google collects reviews from. May be instead of getting a lot of reviews for google places directly I can think about getting reviews for these sites and hopefully these reviews will then spill over google. what do you all suggest?
where can i find list of such sites?