This is one of the items that is tested in your Windows 8 App when you use the WACK.
If you are in Southern California, please email this post for more information on getting a token for your app by June 30, 2012!
Users will always have information they want to share.
If your app implements the share target contract, it will always be one swipe away for the user.
If you want to increase the usage for your app, and have scenarios that can consume data from other apps, implement the share target contract. Windows does most of the heavy lifting with sharing the data, you simply have to receive it and let the user access it within your app.
For more details, check the guidelines for sharing.