What are the limits for posting in Facebook done by an app ?
 

Hi guys.

Let's assume there a website «somesite.com». One can login into it using FB app,
only after he gives needed permission to site's app: «somesiteapp». The application also requests permission to post on friends walls.

Furhter, when above user "John Smith" logs into the site, the app posts X messages
on friend's walls (only once to each one of them) informing them that their friend John registered at «somesite.com» (with hyperlink to the site).

Now, the questions.

1. To how many John's friends can the app post at once - 5? 10? 100? What are the limits?
2. There are many users like John registering daily. Is there total limit for messages, app can post per day ?
3. How FB treats above situation - is it treated as spam or is it legit ?

Thanks a lot in advance, really appreciate. Couldn't find any official answers in FB manuals.