Bitcoin educator and entrepreneur, Jimmy Song, has posted on the benefits (or lack thereof) of a diverse cryptocurrency portfolio. He suggests a fresh argument as to why adding altcoins to a portfolio with Bitcoin makes little sense.
In a stock market scenario, the reason for diversification is to reduce volatility and optimise your risk/reward ratio. In buying 10 stocks instead of one, you hedge against any catastrophic failing in that one stock. Although the stock is also subject to certain transparency requirements, so its story and reality are likely to correlate pretty closely.