Name: Facebook Apps
Reference: Facebook
Need to Act?
Do not lightly contribute to the viral invitation campaigns applied by many apps.
Send invitations only to friends about whom you are confident they may like your initiative.
App's secure their user-registrations by obtrusive (viral) invitations via friends who have registered. A registration is followed by a request to invite all your friends. If you are not concerned about your friend's freedom to explore by themselves what they like or not, then you may be inclined to continue the chain campaign.
Description
A lot of App's are provided for Facebook (and for other platforms)
Availability
To all Facebook account holders (and some also to others who don't own a Facebook account).
Call to Action - #ACT4SDGs
If you receive such an unwanted invitation, it is not evident how to block it.
How to Block Apps
One option that is sometimes offered is to open it in the App Center, there you can block it.
An overview of options is listed here http://www.facebook.com/help/121070141307903/