Actually, most of what you hear regarding the tax law are truisms - with very little basis in fact.
The $600 limit, is the amount after which a payer is required to report the payments to the IRS (in many but not all cases). This does not mean that an amount under $600 is tax-free to the recipient.
In fact, according to the tax law, you are required to report ALL income, regardless of the amount.
In practice, many people ignore this fact. It's your call, of course, but please don't feel that you're "fine" because the amount was under $600. I've seen people get caught for less than that - which means besides the tax, they would now be obligated to penalties and interest as well.
(Again, this is relative to US tax law only)