Maybe Microsoft could try a challenge of uploading a review to Yelp from your Windows Phone. The lack of apps and full functionality as compared to their iOS and Android equivalents is crippling.
For example, the new Angry Birds launched on iOS and Android, and has no plans to port to WP7 due to the need to rewrite it for that platform,
http://www.bloomberg.com/news/2012-03-22/-angry-birds-space-...
You can't submit reviews from an iPhone either. The functionality doesn't exist.
Go to a yelp entry, "Add" and "Draft a review".