Your income from selling online becomes taxable when your profit is 50 cents or more. It makes no difference whether you get a 1099 or not. Getting a 1099 is not what makes the income taxable.
However, if you sell personal items at a loss (i.e. you sell something for less than you paid for it), you have no taxable profit (and you cannot claim the loss). But if you get a 1099 you will have to report the income on your tax return. It can be reported as "personal items sold at a loss" so that you don't have to pay tax on it, but you still have report what's shown on the 1099.
These are federal rules. They are the same in all states.