I saw it in my Nami wallet, is it necessary to add collateral?
To make Smart Contract transactions on Cardano it is necessary to set collateral in the wallet.
But what does it do? Since it is not present in other wallets like yoroi, i wonder in what situation the 5 ada in Nami will be used/spent?
A (larger) bit is explained here:
As far as I understand, the 5-ADA-thing of Nami is not a must. They do it to reduce the risk of losing the collateral (when using a broken contract).
You could put a UTxO with more ADA as collateral, but then that might get lost. So, Nami transfers 5 ADA from your wallet to your wallet, which only fragments your wallet more and costs a little transaction fee, but does not change the balance more than that.
The other wallets are not as far in implementing the dApp thing, so probably have not decided how they will do the collaterals.
And Namis way is not perfect, either:
So, it seems to not work well, when using several Nami instances and it would also totally break, when using other wallet apps on the same wallet.