Transfer blog has a large collection of the anti-sit technology, which uses spikes and what-not to make darned sure you aren't sitting, skateboarding, or getting some steam (see above) on a choice piece of urban real estate.
http://www.usemenow.com/web-log/archives/the_antisit/ - via Cliff Pickover's Reality Carnival
It just looks really unfriendly.
Why not just put scarecrows next to the fire hydrants?
Someone in my hometown has recently put up benches at some of the public bus stops (There were no bus benches at all before.). I ride the bus and was happy to see the benches go up, but then a took a better look at them. They're the type with the big divider bumps in them to discourage people from laying down on them. That's just sad. The benches are looking for advertisers for the signage part of the bench. I can't wait till they hit my business up and I get to give them a piece of my mind.
I should make an "anti-spike" city seat cushion for the elderly. Hard puncture-proof top layer (with soft cover), with softer foam under-layer for the spikes to puncture/anchor into (so the seat dosn't wobble).
You'd have to be a complete jerk to refuse a tired person a place of rest.