In the past you may have blocked wall posts so you wouldn't get fuel, goods, and other random things from your applications. But you may wish to rethink this, at least for a while as the new truffle hunting feature requires wall posts.
To send truffles, your neighbor's must enable their friends to post on their wall.
Likewise, to receive truffles you sent out, they must be able to post on yours.
Go to Privacy settings
Click customize settings
Step 1 Open 'Posts by me' to all
You can set this so all your friends can see your posts, or just Farmville/ certain people. Up to you!
Not entirely sure this is necessary, but it helps to have more things open for sharing.
Step 2 Enable friends to see wall posts
In the next section down, enable friends to post on your wall. Pretty sure this is necessary to get the truffles posted on your wall!
You're done! You don't need to click save or anything. Just navigate back to your main page and play as usual. Hope this helps you get more truffles!
Remember: It takes a little while for all of facebook and zynga's servers to recognize the changes, so you may still have problems for a day or 2.
Feel free to share this with neighbors who have problems finding truffles too, especially if you get the 'cannot post to user's wall' notice!
Next lesson: A guide to help your inactive neighbors delete the farmville app so you don't waste items, time and gift requests!