Spam in your real mail box which even at a quick glace effects:
- waste management resources
- recycling resources
- extra work for USPS (sorting, shipping, delivery)
- extra weight == more gasoline required
- environmental issues (litter, printing chemicals, trees = cut down)
And that is probably just the tip of the ice-berg on actual impact... nope, not an issue, this is how we make money.
I've had a problem with this for years, but there is no way to fix it besides charging the producers of such "mail" an arm and a leg.
Maybe we should push for the death of "Mailbox Neutrality"... or wait, should we support it so they'll kill it off?...
/rant