Are warranties transferrable when you buy used gear?

If someone says the warranty card is blank, they could have just registered it online. So, is the remaining warranty still good to the new buyer? Do you need the original receipt?

When some brands come with a longer than one year warranty ...this could be a deciding factor on whether the used price is worth it if you lose out on 4 or 5 yrs. of warranty ....or it could be bargaining power to get the price down.