The recent community initiative with the highest impact I can think of is surely what Platonides and other members of the global (technical) community did on pt.wiki. Platonides noticed a configuration error on pt.wiki: CAPTCHA was required for all edits since 2008. The error was fixed in April. https://bugzilla.wikimedia.org/41745
Fresh stats produced by the WMF show that in May and June this produced a decrease of overall vandalism (or rather, of reverted edits) with a shocking +58 % increase of productive edits by IPs and +23 % for registered users. It seems pt.wiki may see the end of the decline after many years. :) https://pt.wikipedia.org/w/index.php?title=Usu%C3%A1rio(a):HAndrade_(WMF)/Pesquisa_Vandalismo/Segunda_Fase&oldid=36301585
Discussion is ongoing on how pt.wiki will address this growth. Part of the community may think that "nao estamos preparados para crescer". https://pt.wikipedia.org/wiki/Wikip%C3%A9dia:Projetos/Wikip%C3%A9dia/Reuni%C3%B5es/Reuni%C3%A3o_IRC_21-06-2013
Nemo