My friend Bob Klingel forwarded me a link to an interesting Gizmodo story about mystery stop signs in Cranston, Rhode Island. According to the article, the city has about 650 "undocumented stop signs" (the city probably shouldn't have used the word undocumented – my favorite comment on the article – "These stop signs are stealing the jobs of good, honest, American crosswalk guards"(Edit comment)).
The city doesn't have any paper trail on who installed these signs or why they were installed. The article suggests residents may have put up some of the signs.
I had a resident nail a 2×4 to the road in front of his house as a homemade speed bump when I was the traffic engineer in Maple Grove (we pulled it up within a few hours of finding out about it).
Do it yourself traffic control isn't unheard of, but I recommend leaving a few cars parked on the street to create pinch points and maybe throwing a few tricycles along the curb to warn drivers kids are around. Trikes are much more effective than the cheesy "kids at play" signs you can buy.
I hope the rogue sign installers called the utility locating company. It would be quite a news story to have some guy hit a natural gas main while trying to put up his own stop sign. And it must have been difficult to buy stop signs before the anonymity/parcel delivery provided by the internet.
I've posted about the federal requirements for cities to keep track of their sign inventory. The amazing part of the article is the city will probably leave 95% of the signs. In this day of huge budget shortfalls, my goal would be to prune as many signs as possible to reduce the maintenance costs.