After I recently went through a huge picture collection (80000+ items), I found that my home partition was missing 2.5GB of space. I really didn't have a clue what that was all about so I checked du | sort -n. Apparently, the culprit was the hidden thumbnails folder under /home. I first tried a simple rm * but that failed because of "the argument list is too long". I had to drag the folder to Trash to get rid of it.

Does anyone know whether this is normal behavior? Are those thumbnails actually supposed to remain there in order to boost performance ?

Edit: is there any way to edit the title of posts on LQ? I slipped in "icons" instead of "thumbnails" but I don't see a way to correct it...

Kind of, yes. It allows faster loading of webpages (and filemanagers like Nautilus) as they don't have to retrieve the icon again and therefor can render the page quicker. Does it hurt deleting it? No, but you'll find it soon comes back