Suppose you meet a guy from an lesser-known hedge fund. Perhaps a quant strategist, a quant developer, a high frequency trader, a fund manager or the CEO. He could be full time running multiple funds for a few years, perhaps with multiple investors in his funds. How do you know he is not an unemployed high school dropout running his one-man operation out of his parents' garage? His investors might be relatives + friends.

The real evidence is asset under management. Anything below $10m is a tiny fund.

Now you meet another guy, from a HFT software vendor. This time Real evidence is company revenue. If not, then big-name backers.

A simpler evidence of track record is past salary.

In conclusion there are too many people with big words in the resume, but only a fraction having credible track record (brank).