Haha, this is so funny. This is when I don't dismiss it, because I target my ship as a way to tell how far I've gone (for exobiology, distance matters).It depends on scenario. If I'm picking flowers I will so I can recall it without having to backtrack.
Lately, though, I've been using MattG's cool plugin that pops up a message when I've gone far enough away from the last sample -- that's a nice feature.
MattG's Observatory plugins
Quite some time back now, Vithigar mentioned he was working on a new version of Observatory that would allow plugins. This immediately piqued my interest, and I've been watching the project progress with anticipation. Now we have our hands on the new version I've been busy writing some plugins...