This paper presents an efficient sharing protocol (iShare) that blends different wireless interfaces of the mobile device for content dissemination service. With iShare, mobile users download content from a source via the cellular link and at the same time form an ad hoc mesh network for peer-to-peer exchange of content data. The mesh remains robust to network dynamics, minimizes ad hoc communication overhead, and parallelizes the downloading process among mesh members. In order to counter selfish behavior and balance the download among mesh members, we apply a practical "tit-for-tat" incentive mechanism, which exploits proximity and mutual content interest of mobile users. We simulate, evaluate the performance of iShare and compare it to other content dissemination schemes using cellular broadcast channels, cellular unicast channels, and tree-based protocols. The obtained results show that iShare significantly outperforms alternative approaches. The results also confirm that iShare enables users to continuously obtain data via ad hoc connection during the cellular handoff period, and provides multi-homing download for groups spanning adjacent cellular cells.