said 1 year, 3 months ago:
If you are talking about an app, that runs inside a facebook fan page… then the answer is no, they cant mess up your fan page. This is because they run inside an iframe.
If you mean, can they “mess up” your profile page, well, some apps can post to your profile page… and may make it look messy (but not likely). However, thats one of the reasons facebook now organizes apps into sections on your timeline.
An example of an app on a fan page is http://www.iwipa.com my company owns this one. It allows you to create mini web sites within your fan page.
It doesnt harm your page, the purpose of this app is to enable you to enhance your page.