Then those users get what they deserve for using a closed source version, while a reliable open source/MIT version would still be available.
Oh gosh, I have to calm down ... it really is hard for some people to grasp this. Please listen to yourself, you're saying that using closed source client is a bad idea, do I understand that right? And you are encouraging people to use the open-source MIT one over the closed source one, right? That means people should really use only the open-source version to not get screwed ... what. is. the. point. of. the. MIT. license. then!? The MIT license is specifically designed to allow for closed source derivatives! If you're saying that people should only use open-source one without the risk of getting "what they deserve" if they don't ... you are in total agreement with me and you are making the exact same argument for using GPL as I am. Why do you feel the need to make excuses for MIT license then? Do you not like me personally that you just have to disagree with me for some reason? Or is this some ego thing about "winning an argument" or something? I honestly do not understand why people do this, it's frustrating. You may not like me, you may not like my style, you may enjoy arguing or whatever but I beg you to leave that behind and look at the facts and logic instead, please!
If the closed source version is eating their bitcoins they will abandon it soon. There is even the possibility that some person develops a closed source version from scratch and does the same, no MIT/GPL/other license of the current bitcoin client is going to change anything on that.
Ok, one by one:
1) Proprietary version doesn't mean that it will be doing only things that you'll easily notice, it can have backdoors, it can be dormant for several years and then rob a half the community at some point effectively destroying bitcoin (but still making a huge profit for whoever has done this)
2) Yes, there is a possibility that someone will develop a client from scratch, is there any reason you can think of that we should make that possibility much higher by making it easy to do? I love this logic, let's all put wallets on our front porch ... they could just taken them by stealing them in a crowded bus anyway, so what's the harm.
All you've written are excuses to do nothing ... not reasons to have MIT license, you did not say why MIT would be preferable to GPL, you just made excuses for the additional and unnecessary pitfalls of MIT. There is no reason to keep these pitfalls if there are no benefits that outweigh them. I see no benefits to MIT, only unnecessary dangers. The only supposed "benefit" is the possibility of closed sourced forks which you yourself said are dangerous and discouraged. So I really do not see why would you have any rational reason to disagree with me.