Rabbi Shimon Shwab's letter on the Manhattan Eruv. He doesn't really discuss the Halachas behind it, just the potential danger to religious observance.
Note, that the original plan for the Manhattan Eruv was to use the Island itself or the buildings around it as a wall, so many of his claims only apply to Manhattan (or other islands).
But one of his points is that since people don't know (or care) about Shabbos technicalities, "If they will stroll on bridges on Shabbos, say from Manhattan to the Bronx, will they obey [the Rabbi's orders] to empty their pockets on the way? Will they understand the concept of Tzuras HaPesach? [Will they know] the borders of the Eruv? Until where can they walk and when do they have to stop?"