I'm still not sure I agree. Yes, theoretically in a situation where the flight is sold out and VS have pre-selected all seats on the flight you wouldn't be able to select any seat at all. But I think most people understand that when you buy a Light fare or any fare which doesn't allow seat selection until check it, the risk is that you won't get what you want.

If you look at the sales page for Economy Light, I think they are pretty transparent about the situation. VS do clearly state that your seat will be automatically assigned at check in and that you may not be able to select the seats you want. If it is accurate that seats are assigned at check-in, the above scenario would only occur if you were the last person to check in in the cabin.