Every time user successfully receive data from your greed station you earn 1 trust. If within 15 days your wallet will not earn at least 1 trust you will be opted to force sync to test integrity of your storage file contents. If it passes that you earn 1 trust point and continue working. If, however your storage integrity will fail your wallet will not be able to participate in storage sharing. Staying offline for too long will freeze your trust rating. Every several month of positive trust will be rewarded by incriminating your trust coefficient making you eligable to offer your storage to those willing to pay for extra safety.