Are the app store / Google play rigged?

Judging from links like this http://fiverr.com/gigs/search?utf8=%E2%9C%93&query=app+store&x=-1198&y=-125 it looks like there are quite a few people tying to game the app/play store. This looks like the tip of the iceberg. Taking the idea to its logical extreme I imagine call centers full of people in some third-world country solving captchas and posting positive reviews 24/7. So is this as much as an issue as my speculation leads me to believe, or are Apple/Google taking steps to prevent this?