Bumper stickers seem to be an endangered species these days, at least in the San Francisco Bay Area. Many demonstrated a person's political/social views, providing passing interest on a roadway. With the decline in bumper stickers, a new way of marking affiliations and views has emerged -- address labels.
One can order, of course, address labels from commercial sources, which offer a mulitiplicity of designs. I did order some a few years back, and that opened a floodgate. I now regularly receive mailings from a variety of non-profits and and other groups sending me address labels and asking asking for a donation. The labels can have a mixture of designs, only some of which have the organization's logo; others have messages/logos only. I think there must be a merged marketing list somewhere of people who have ordered address labels and people who fit some non-profit's profile. Or they're merging the lists themselves.
A few days ago I received a letter at work with an address label I recognized: "Teach tolerance" with a logo. That person and I are both on at least one mailing list.
It's not quite as much fun as reading bumper stickers, but I'll take my cultural markers where I find them.