Yeah some problem here, my thumbdata is only about 1gb but i don't have a ton of photos on my phone, i can imagine this file getting bigger if there are lot's of photos on the phone.
Deleting the files will not solve the problem as android will recreate them very fast. I see and understand the purpose of the thumbdata files but there should be a way to set max size and location for this files...
IF anyone figures a nice solution for this problem please post
Edit: just had an ideia, maybe we could move the folder thumbnails to external sdcard and use foldermount or links2sd to link it to the internal memory? i can't test this right now cause i'm at work but i'll try it later if i have time.