Chainfeed not working $unwriter (July/1/2018). Please don't forget about it now with your BitDB project. Chainfeed is the real-time Maple Syrup on my Memo Pancakes.
Sorry there was a problem with bitcoin node so had to redownload the entire blockchain. chainfeed is as important as bitdb, many apps already use chainfeed api, such as chainbet.
Sign up implies making an account with a trusted server. You don't *need* to sign up on memo.cash, you can just use your private key on any OP_return compatible wallet to make memos.
memo.cash isn't the only way to read/write memo data. There are a few other clients, but the only wallet I'm aware of is the Telescope wallet, which is a browser extension