Proper etiquette would be, don't walk or run in ski tracks. Mohonk Preserve has signs all over the place admonishing people not to walk unless they have snowshoes, but there's no enforcement. The tracks I put in in the my local parks get demolished, mainly because the suburbanites don't know better. Interesting how I see snowshoe tracks alongside ski tracks, and the boot hikers or runners are right in the ski tracks.
Snowshoes designed for trail running are hardly better than running with shoes alone.