Adopt the EURO now?

There's an interesting article on EPL today that talk about Estonia adopting the EURO as a parallel currency to the Kroon. All sorts of transactions such as payroll and taxes could be done in either currency. This has been brought up because it's clear that Eesti won't be joining the Eurozone anytime soon as inflation continues to rise out of control and the government is incapable (or unwilling) to address it. Two of the ruling parties have talked about this and it appears to be something that is under study and consideration, how serious that consideration is is unknown.

My thinking is why not take it one step further. Why not simply abolish the Kroon and adopt the Euro unilaterally? There are a number of countries that use the US Dollar even though there not part of America, so why doesn't Eesti make a similar move? There may be EU laws against it, I don't know, but it may be worth considering.