Eric Goldman offers a terrific--and concise--summary of Section 230 and how courts have recently interpreted its grant of broad immunity to online intermediaries, most notably:
47 USC 230 tries to divide online content into first party content and third party content. In its simplest form, 230 says that online actors can't be liable for third party content unless (1) ECPA, (2) federal criminal enforcement, or (3) IP claims.