Adaptive filters are at the core of many signal processing applications, ranging from acoustic noise supression to echo cancellation [1], array beamforming [2], channel equalization [3], and to more recent sensor network applications in surveillance, target localization and tracking. A trending approach in this direction is to recur to in-network distributed processing in which individual nodes implement adaptation rules and diffuse their estimation to the network [4], [5].Ranging from the simple Least-Mean-Squares (LMS) to sophisticated state-space algorithms, significant research has been carried out over the last 50 years to develop effective adaptive algorithms, in an attempt to improve their general properties in terms of convergence, tracking ability, steady-state misadjustment, robustness, or computational cost [6]. Many design procedures and theoretical models have been developed, and many novel adaptive structures are continually proposed with the objective of improving filter behavior with respect to well-known performance tradeoffs (such as convergence rate versus steady-state performance), or incorporating available a priori knowledge into the learning mechanisms of the filters (e.g., to enforce sparsity).