If you're underage then definitely use your social... You get an automatic standard deduction, so unless you've got another job somewhere, you're safe as long as you make less than $4,000 or so.
You have to claim income, technically, no matter the size. Google will automically report to the IRS any income over $600, but the right thing to do is to report any amount no matter what.
Mind you, not a tax lawyer, fool.com has a free bulletin board system with tax advice, might check out their opinion.
-Allan