This paper discusses the role played by Opportunistic Networks (ONs) as a means to bring Future Internet services to users in different situations. After the identification of technical challenges associated to the operation of ONs the paper focuses on their applicability in the coverage extension of a wireless network. In particular, the flexibility offered by the availability of multiple spectrum bands to select for the set-up of the ON link is analysed. Results in a scenario with 2D correlated shadowing are obtained to illustrate how a proper spectrum selection influences on improving the coverage extension capabilities.