Wetbags are designed for storing cloth diapers until washing day. We have several that we use for that purpose as we cloth diaper and cloth wipe. However, they are useful for so much more than that!
We have a wetbag that hangs in the pantry that holds wet wash rags, dirty bibs, dirty towels, dirty napkins, etc. until it's full and I run it all up to the laundry room on the second floor.
We have a wetbag hanging on the back of the laundry room door to store dryer sheets that are used up until it's time to make another large batch of them.
We have a wetbag in the diaper bag holding all of the diaper changing materials. If there is a blow out, all of the dirty clothes/diaper/etc. can go in the wetbag and the leftover wipes and such can be loose in the diaper bag.
We take a wetbag if we go somewhere where getting wet is expected - the pool, to play in snow, to play in a friend's backyard, etc. This stores wet towels, clothes, etc. until we get home without getting carseats wet.
When Meghan has a bad cold, we use rags to wipe her nose rather than tissues which will irritate it. A wet bag (especially useful are wet/dry bags) is a perfect place to store dirty wipes wherever we are until they can be dumped in the laundry room to await an appropriate load of wash. A wet dry bag allows us to store clean and dirty wipes together to move between locations in the house.
When the day comes when we are no longer cloth diapering, we will not be getting rid of our wetbags. They are far too useful!
*Note* I linked to Planetwise wetbags for our large wetbags - each of them have had the handle pull apart from the bag and I have had to sew them back on. This seems to be a consistent problem with the bags, but their usefulness is worth this small problem to me!