Pew Center report finds that online civic engagement is largely the product of the same people engaged in offline ways -- those who with higher incomes and greater education. In other words, online or offline, the song remains the same. The graph to the right, hotlinked from the Pew site, says it all.
The largely parallel lines suggest it may be time to stop separating offline and online participation and just fold them into a single measure of political or civic participation.
It's both a theoretical and methodological question, one worth pursuing.