The main purposes of marking an answer correct is to let others know that a solution exists if they are searching for an answer to the same or similar issue/problem. When one views the Discussion list, questions that are marked answered show with a green bubble and a check mark. Unanswered questions just stay blue with a ? mark inside the bubble and non-question messages (announcement or info) just show as grey bubbles.
Points are still awarded in the [explitive deleted] social scheme at the core of the new version of the Jive software.