I haven't join gridcoin yet but I have a small comment. For cryptographers, it makes sense to have the actual cost of bruteforcing something, specially it gives you an idea of how fast/expensive you could run such a computation in a decentralized way. It is because people tackled the RSA challenge that we still believe RSA2048 to be usable.
That being said, it doesn't mean the project is useful or not.
RE: On the Gridcoin Whitelist, and Where to Draw the Line