Enormous amounts of knowledge sharing occur every day in community question answering (CQA) sites, some of which (for example, Stack Overflow or Ask Ubuntu) have become popular with software developers and users. In spite of these systems' overall success, problems are emerging in some of them--increased failure and churn rates. To investigate this trend, researchers conducted a case study of Stack Overflow. First, they evaluated the community perception that the emerging problems are heavily related to the growing amount of low-quality content created by undesired groups of users (help vampires, noobs, and reputation collectors). Reproducible data analyses of content and community evolution supported these findings. Suggestions to deal with the emerging problems include providing users with responder-oriented adaptive support that involves a whole community in QA. Such approaches represent an eminent attitude change regarding QA support, with the aim to preserve CQA ecosystems' long-term sustainability.