I used to frequent Quora and stopped specifically due to this. Leave a few answers on popular topics, especially about apps, and your inbox is flooded with requests to answer questions like "Is it true that X company is the most amazing and affordable software development outsourcing service?" and "Why is Some_Random_App much better than Popular_App_That_Our_App_Copies?". Sometimes they were brazen enough to post questions about X app with names like XMary or XJohn.