AngelList does not take a cut of your raise. The exception is if you use "Invest online," where AngelList creates an LLC to pool multiple smaller investors into one. In this case you pay no fees, but your investors would ay a 10% carry to AngelList.

I'm going to suggest a few ideas that are off the beaten path. Besides buying and holding Bitcoin (which I think is a good bet over the long term):

1) Start a mining pool

Bitcoin mining is finished for the little guy. You need to prepay for expensive mining rigs that quickly stop being profitable once you finally take possession.

But almost all miners need to use a mining pool. Most pools look amateurish. Talk to Bitcoin miners and find out what they're missing and build it. You will get to skim a nice 2-3% off all the mining profits without investing in expensive mining hardware.

2) Lend money to Bitcoin traders

Don't have the stomach to risk your money by investing in Bitcoin? You can profit by lending your money to people who do.

Bitfinex.com allows you to do this. You can currently lend out USD at 200%+ APR to people who use it to buy Bitcoin on margin. The risk is low to nil as the loans are backed by the borrowers BTC and Bitfinex will close out their position and repay you if the value of their holdings drops too much.

Call me if you want to get feedback on your ideas.

You just answered your own question by admitting you can't "protect" your product from copycats. So just accept this and don't worry about it.

A copycat will always be a step behind. They can copy what they see on your site, but will never understand your thought process or customer learnings that inform your product decisions.

I have never (ever) seen a company fail due to copycats.

Focus on 1) Delivering an awesome experience to your customers and 2) Finding as many of them as you can; and you'll do fine.

Happy to discuss in further depth on a call.