Violating some companies ToS might not be legal in my country. E.g. steam does not allow me to sell games I bought there. My countries laws however are pretty clear in that regard. I own that copy of the game and it is my right to sell it. Steam does not allow me to sell an individual game. Selling or buying a Steam account is thus not illegal in my country but at best in a grey area and whether the sale would break any laws would have to be determined in a courtroom. Trading PayPal accounts might be similarly a grey area in certain areas of the world.
in case of steam don't count on this!
in germany (where i live) tos doesnt count too (any text presented AFTER i paid is nothing), but if steam sees someone selling his account they just ban him regardless.
they argue that you did NOT buy the game: you just lend it.
i've not yet seen someone buying a dvd, register it through steam and tries to sell it. if he goes to court he might win (but ONLY if he did buy it in a shop - NEVER for games bought in steams online shop page, because they clearly state they only lend them out)