When I was young, my family made me put all of my christmas/birthday money into the stock market. Intel was suggested by an adult family member who did not have a tech background. That made up a majority of my portfolio. The rest of my portfolio was allocated to a stock I chose, Apple.

Reason for Apple: At my elementary school, everyone loved using the Power Mac G5's during computer lab. Every kid had/wanted an iPod or iTouch (and eventually iPhone).

it's very risky to not diversify your stock portfolio.

The scenario being discussed is a college student with a "portfolio" funded by birthday and Christmas presents.

It makes sense to be less risk averse in that situation than a mid-career software engineer with a family to support planning for retirement.

Plus trading fees would swallow a small principal

This is a common misconception. If the amount you invested is small enough that it doesn't matter, or that you can easily replace it, then the downside risk doesn't matter anyway.

If you wait long enough (and you should be investing for 10+ years from now) doing things that hurt growth doesn't risk you losing money, it guarantees it. And diversification hurts growth because of transaction costs.

Still, probably better to buy SPY.