Short TCP flows may suffer significant response-time performance degradations during network congestion. Unfortunately, this creates an incentive for misbehavior by clients of interactive applications (e.g., gaming, telnet, web): to send "dummy" packets into the network at a TCP-fair rate even when they have no data to send, thus improving their performance in moments when they do have data to send. Even though no "law" is violated in this way, a large-scale deployment of such an approach has the potential to seriously jeopardize one of the core Internet's principles -statistical multiplexing. We quantify, by means of analytical modeling and simulation, gains achievable by the above misbehavior. Further, we explore techniques that both misbehaving and regular clients can apply to optimize their performance. Our research indicates that easy-to-implement application-level techniques are capable of dramatically reducing incentives for conducting the above transgressions, still without compromising the idea of statistical multiplexing.