it's very good question.
but you just can activate it online on
1 pc then you can't activate online on other pc.
this is OEM rule,this activation codes are sensitive to motherboards. you can find many ebay seller that claim their stickers obtained from useless
PC and laptops.but it's impossible because you must have that motherboard to use stickers
they usually buy Retail key and print as sticker
to ensure is this keys and stickers genuine or not please look at this screenshots:
my received code from supplier
screenshot by customer after activation
key and Product ID perfectly matched!
this keys(stickers) are new and you can check with microsoft online support that is it valid and unused or not