It was relatively harmless in the old days when it was cardboard and twine, and of course there was no internet to get your message out back then. But now it's plastic posters, plastic ties, none of it recyclable and usually the ties are left there to poke the eye out of unwary tall people (it's ridiculous how many posters get crammed onto the more popular lampposts in Dublin city centre, so the bottom one is often at head height)
Then there were some truly offensive posters in 2015 and 2018 from the No side (I would have said 'sides' but it's always the same crowd) displayed prominently for weeks on end. A particularly explicit one went up right outside my kids' primary school during the abortion referendum campaign. It didn't last the night... this in what for years has been a voluntary no-postering area which works well. All of the approach roads to the village centre always get plastered with posters though so overall the number of posters in the area is the same...
About 15 years ago a sitting TD in my constituency had the "brainwave" of making her posters (text-only, no picture) in the shape of yellow diamonds the same size as a road sign, how flippin' stupid was that?