[quote name='ZForce915']Can you tell how many shares are left on an account at any time?[/QUOTE]
That depends on how you look at it. Theoretically, you could, if you have 5 PS3s in your possession.
If, say, you bought some games, shared with 2 people (so 2 shares left), and want to make sure that for the remaining two shares that whoever you sold them to only uses one, then you would only need 2 shares (given that the first 2 shareholders don't spill the beans).
Well, that is some simple logic, I don't mean to say that you weren't capable of thinking of it yourself, just that this is the only real way to tell. You'd have to, of course, disable the "counting" PS3 users before selling a share or two.
If someone actually has the tools, they could use up 5 shares themselves, and then when they find a seller, delete one user, and when they find another, delete another user - but nobody's going to go through all that trouble. Most people are trustworthy, especially when the games are so cheap split 5-way.
In short, yes there is a way to tell how many shares are left, but that would require multiple PS3s, and a sole entity in control of them.