Varian et al. (2005), for example, give a nice summary of the role of the federally spon-
sored “Do Not Call” list in preventing potentially intrusive direct sales calls.
An open question is whether the ability to use data to enrich advertising leads not just
to ineffective advertising but also to negative welfare outcomes. This is an important
question because one of the critiques often made about the new digital economy is that
it leads to information silos, where Internet users are compartmentalized and conse-
quently not exposed to potentially welfare-improving information.
Gentzkow and
Shapiro (2011)
find that while online news consumption is more segregated than offline
consumption of local news, it is almost as much less segregated than offline ...