I know exactly what you mean about benches, M0nica - last year we spent a few days near Bridlington (don't ask!) and there were what felt like miles and miles of these things along the coast.
Personally, I have decided that I don't want any sort of memorial. I would rather that my ashes were scattered in a favourite place, where any family who remember me might take a walk if and when it suits them, and pause for a moment to enjoy the solitude of that place that I loved and perhaps briefly remember me at the same time.
I scattered my dad's ashes in that same place only a few weeks ago, as it was a place he loved too, but was slightly nonplussed (sorry, can't think of exactly the right word, so that one will have to do) to spot a memorial bench very close by. I don't begrudge that person's nearest and dearest their right to remember their own loved-one in the way that felt right to them, but if many more were to appear, the place's magic would be totally lost!