I have a problem with my viral apps... I use PHP SDK api (post to feed) to place ads on the walls of 20-25 friends of the installing user. It worked nicely a couple months ago: the apps went viral after 5-6 seedings and super-viral in a couple days. But now I have a dozen apps seeded about 20 times each and virality is still zero. Testing showed that ads do appear on friends' walls but don't show on their friends' news feeds. Looks like I missed something... Any ideas, suggestions? Thank you.