How P2P Lending and CDs Are Similar
The key similarity both investments share is that both require you to tie up your money for a certain, specified amount of time. As such, both are essentially illiquid investments.* However, this length of time is fairly short-term, particularly when compared to 30 year bonds, for instance.
For CDs, your money can be tied up anywhere between three months and five years, depending on how long you choose to invest. For P2P, (which I'm basing on my experience with Lending Club, as I am unfamiliar with Prosper and others), your money is invested for either three years or five years.**