> So I can just buy one "poisoned" bitcoin and send a tiny fraction of it to every public address I can find. Now the entire network is poisoned. Only if these

> So I can just buy one "poisoned" bitcoin and send a tiny fraction of it to every public address I can find. Now the entire network is poisoned. Only if these tiny fractions are actually used. When you send something to a Bitcoin address, what you are actually doing is creating an unspent transaction output which can only be spent by that Bitcoin address. Nothing prevents the wallet software from ignoring that tiny fraction and instead using a larger unspent transaction output to the same address, which would result in a smaller transaction (one input instead of two, since the tiny fraction most probably wouldn't be enough for the transaction).