Lodsys is suing developers using the App Store In-App purchase function:

http://www.macrumors.com/2011/05/13/lodsys-threatens-to-sue-app-store-developers-over-purchase-links/

Update: Apple states that they licensed the patents in question: http://www.9to5mac.com/68561/apple-makes-statement-on-lodsys-patent-claims-says-developers-are-covered-under-its-license/

Update 2: Lodsys doesn’t agree on Apples statement as they posted on their company blog: http://www.lodsys.com/blog.html