<i>Angel investors can expect favorable payoffs with only 10 deals, but it takes at least 20 investments to truly be safe.</i><p>Taking this to heart might get dangerous. The benefit of going from 2 to 20 deals exists only if the quality of the extra deals remains high - but what are the chances of that happening?<p>An angel that's doing a few investments would be cherry picking from a moderately larger deal flow, and so each extra deal would almost certainly be a step down in quality.<p>I'd say that doing math like this is a bit of a leaky abstraction, and it could just as easily cloud judgement if not taken with a large grain of salt.