Huge size on mongodb's gridfs. Should I compact?
You have few options here.


Run DB command 'Compact' on the collection - This will not reclaim disk space, but will perform defragmentation over the specific collection.
Perform a repairDatabase - This reclaims disk space back to the OS. the repairDatabase runs over the entire DB (or shard) and not just one collection (I would read the documentation, as repaireDatabase both locks the DB it's repairing and requires at least x2 of disk space than your DB size)


Please keep in mind that MongoDB always seeks to allocate more data files.
If indeed as you mentioned, you're deleting a lot of data, Mongo will reuse this space but it might contain 'junk' blocks which makes mongo use less than it actually has allocated. this is why Mongo is allocating more and more data files.

You can read more about it here: Managing disk space in MongoDB

Hope this helps a bit.