If Trainn sends you $600 or more worth of items, they are required by federal law to file a form with the IRS reporting these "winnings"
This occurs because all items you recieve from Trainn are winnings, and technically all winnings should be reported on your tax returns. However, the IRS only requires those providing winnings to report them if they amount to $600 or more. They don't want to bother with added paperwork from every time somebody won $5 from a lottery scratcher. So if you make less than $600 in winnings, even though you are supposed to report it, the IRS has no real way of checking if you made them.
Winnings are income.
That means that you will pay income tax on winnings. Getting $1000 worth of stuff from Trainn bumps the amount of money you made this year up by $1000.
Here are the current income tax brackets:
Income Range: $0 - $7,825
Tax: 10% of the amount over $0
Income Range: $7,826 - $31,850
Tax: $782.50 plus 15% of the amount over $7,825
Income Range: $31,851 - $77,100
Tax: $4,386.25 plus 25% of the amount over $31,850
Income Range: $77,101 - $160,850
Tax: $15,698.75 plus 28% of the amount over $77,100
Income Range: $160,851 - $349,700
Tax: $39,148.75 plus 33% of the amount over $160,850
Income Range: $349,701 and up
Tax: $101,469.25 plus 35% of the amount over $349,700
If you are a student, and would otherwise have 0 income, then you are in the first tax bracket. So you pay a 10% tax rate. If Trainn sent you $599 in stuff, you'd pay $0 taxes on that. If Trainn sent you $600 in stuff, you'd pay $60 taxes on that. $2000 in stuff = $200 taxes. But it isn't really that easy. You also get to take a deduction. If you give a lot to charity, or have other means of getting plenty of deductions, you can itemize your deductions. Chances are this isn't the case, which means you just take a standard deduction. For 2007, the standard deduction is $5350 for single, non-head-of-household people. That basically means you get to erase up to $5350 worth of your income.
So if you otherwise made $0, and Trainn sent you $2000 worth of stuff, you'd still have to fill out the form once hitting $600, but come April of 2009 (when you're filling out your 2008 tax return) your stadard deduction is able to completely erase the $2000 of winnings you got, making your effective taxable income $0. So you pay 10% of $0... which is $0.
Note: if you are claimed as a dependant (for example: your parent still claim you as one), the $5350 deduction described above doesn't apply to you. Many factors can increase the amount you deduct, such as having dependents (kids), being married, paying for your or a dependant's tuition, mortgage payments, etc.
Long story short: if you have little or no income, getting more than $600 worth of stuff probably won't cause you to pay taxes. If you do pay taxes, it's probably best for you to stay under the $600 mark. If you're planning to go way way above the $600 mark it might still be worth it (if you're in the 25% bracket, and get $2000 of stuff from Trainn, you'd pay $500 in taxes on it. But you might still prefer that to getting $550 stuff from Trainn and paying $0 in taxes on it.)
Hope this helps clear things up for people
Disclaimer: None of this is legal advice, and should not be considered to be legal advice.