A year ago we started a program were new mappers - after they did their first edit in The Netherlands - received a welcome message with links to various sources of information on the mapping process, the do's and don't's, the editors and other useful stuff.
I was the initiator of that program and also the one responsible for finding the new mappers ([Pascal Neis provided the necessary RSS feed) and sending the messages. As such it was a one-man job.
After one year and sending more than 1500 individual messages to those new mappers, I will no longer continue with this program.
In my earlier diary-entry on this program some (statistical) conclusions were drawn about the number of mappers and the amount of mapping activity over time. There seems to be no change to this statistical data since that report. But I did not expect to happen that either. Research from others points in the same direction as can be learned from the reactions to that first article.
About 75 persons (0.4%) replied to my welcome-message, mostly with a simple "thank you", sometimes asking for more information. A very small number of people joined (and stayed in) the active mapper group, but most of the new mappers are "one-time-only" mappers. ◊
After maps.me ◊ became available as a simpe data editor for OSM, a great number of people entered the OSM mappers world ◊, but most of them are not aware of the underlying principles and goals of OSM, nor are they aware of the communicating chanels we have (mailing list and forum). Hence, sending a message to those mappers is rather useless because they are not aware of the fact that there is such a thing as a private mail-box in their account. This became the more problematic as a lot of tourists are now acting as "mappers", but given their limited knowledge of mapping and the limited possibilities of maps.me, those edits very often need the hand of an experienced mapper to fix. ◊
During the past year that I have run this program, I learned a lot about the way new mappers behave and what they expect from OSM, and it is my opinion that my welcome message (including links to a number of wikipages in Dutch) did only help in a minority of cases. And in those cases where the help realy was needed (maps.me), I couldn't reach the mappers...
There are maybe other/better ways needed to instruct new mappers on how to do the job, and this might be a topic for future research by others.
 A "one-time-only" mapper might of course return to mapping, years later, as history shows. But it does not happen very often.
 Maps.me is a great app that I use as my on-the-road tool to consult the OSM map and as a routing aid. I would never use it as a serious mapping tool.
 An increase of about 20%
 Other OSM communities experienced more or less the same problems with maps.me, as can be read here, here and here.