In the case of Sia, existing services are unable to take advantage of unused disk on other people's machines that is of little value to them, but more value to someone else - making storage extremely cheap compared to other existing services. The virtual scarcity provided by the blockchain provides a completely decentralized way to sell this storage with no 3rd party involvement.
In the case of Namecoin, it removes the need for centralization of naming services and in doing so prevents external parties from interfering with naming services, the owner decides where it goes, not a registrar, not ICANN, not the US government.
Generally speaking, decentralization is in one way or another the major argument for services done this way. Blockchains enable decentralization of scarce resources - but that's it. We need to stop proposing them for everything when they're really not appropriate for everything.
In the case of Sia, existing services are unable to take advantage of unused disk on other people's machines that is of little value to them, but more value to someone else - making storage extremely cheap compared to other existing services. The virtual scarcity provided by the blockchain provides a completely decentralized way to sell this storage with no 3rd party involvement.
In the case of Namecoin, it removes the need for centralization of naming services and in doing so prevents external parties from interfering with naming services, the owner decides where it goes, not a registrar, not ICANN, not the US government.
Generally speaking, decentralization is in one way or another the major argument for services done this way. Blockchains enable decentralization of scarce resources - but that's it. We need to stop proposing them for everything when they're really not appropriate for everything.