I know some mobile app companies will have a few of their own people write reviews. But if someone from the Yahoo Axis team really sent out a mass company-wide email asking for fake reviews like this, someone is bound to cry foul (and forward the email to ATD).
They don't have to ask for fake reviews. They just have to say "Hey our cool new app dropped into AppStore today. Check it out and review it if you like it." Yahooers might genuinely like it and give it a high score.
It should be taken as a good sign if 900+ employees are still motivated enough to download and review the app.
they can pay contractors on odesk to write these reviews.