Here's a neat trick. I've recently been playing, and enjoying, the online hitman role-playing game gpsAssassin from developer Side Hobby.

It's in the mode of Facebook and MySpace games such as Mafia Wars and Mobsters, but with a locational element, based on your iPhone's GPS or iPod touch's wireless connection/manual location.

I've just received by email this inducement to encourage my feedback via an iTune review.
"Did you know? You can send proof of a 5-Star iTunes Review to joy [at] gpsAssassin.com for $35,000 Blood Money (include your Alias). You can do this for every new version of the game!"

Note: Blood Money is the in-game currency used for buying weapons and armour.

Presumably this sort of thing if frowned upon by Apple but not prohibited.

However on the UK store, the game only has a 2.5 star rating (from 298 reviews), while on the US 2282 reviews give an average of the same rating.

Maybe the amount of Blood Money needs to be increased?
gpsAssassin is free and here's the App Store link.