I'm always keen to see new contributors to OSM. They bring details that interest them to OSM, be it their local area, their sport, their hobby, their work or whatever. Having an open tagging scheme that allows all kinds of objects to be mapped is part of the strength of OSM.
I follow new mappers in my area and sometimes add comments to their changesets or send them a welcome message. Sometimes a new mapper adds one thing and never adds more, sometimes they add one type of thing over wide areas. One thing the East Riding of Yorkshire needs is more fine detail of rural footpaths and bridleways. A few new mappers appeared starting to add footways and I was encouraged that this may spread. Sadly I was wrong and what I hoped was something useful is turning into something less so.
It seems that someone has discovered that some details in OSM may be being used in Pokémon Go, the virtual reality game by Niantic to find imaginary creatures. These imaginary creatures appear more near water and in parks near footpaths. The new mappers were adding footpaths in parks to encourage these beasties to appear. Their new footpaths were in good places and were welcome, but then word spread.
People then started adding more parks and ponds. Some were real parks and ponds that were just missing from the map, but some were plonked anywhere, over existing buildings and roads, over schools or whatever. A few people realised that changing existing areas' tagging was easier, so suddenly a building becomes a park or a pond.
It is not clear to me that Niantic are using OSM data, but if they are, adding phoney stuff won't work very well because it will be found and cleaned up quickly. If Niantic are using OSM data they will probably only incorporate changes to OSM data occasionally, if at all.
It's great to see new mappers. Maybe a few will become more interested in mapping than Pokémon. All the real parks, paths and waterways that are being added are all helpful. Tidying up the junk is nuisance but maybe I'll spot other stuff to improve too.
Back to the new users feed. Oh, there's another one ...