I've had the opposite experience with Crashplan. Their software does take a lot of RAM though. I'm happily storing 3TB on their servers for $5 a month (yearly). I don't think that's such a bad deal.
IMO, Crashplan's service is terrible. On a university network I was never able to max out my upload. With BackBlaze I was able to max it out. Crashplan's built on Java, which is the reason for the RAM usage, while BackBlaze is native to OS X and Windows.