make it more difficult to earn profits! have the potential risk be in line with the potential rewards. this is why starbonds are such a no brainer. very little risk (the whole damn market knows a future price for certain) and big potential reward (if the price is way away from the future TAG).
removing share limits will make the game more difficult. especially on moviestocks. if some schmuck with a huge port thinks AVATR will only do $10 million opening weekend, let them short the crap out of it. if he shorts 100,000,000 shares and drives the price down to $30, what will happen, in due time? the market knows better and will step in and absolutely crush them! (these losses will take cash out of the system) yes, this opens manipulation gate a little more, but people will learn quickly. (and if they do manipulate, you can fine them, thus taking even more cash out of the economy). as for the integrity of the data, you can always temper the volatility around halts.
so, to recap, removing share limits will do 3 things, IMO- it will make the game harder, it will increase the risk, and it will ultimately take cash out of the economy with losses and fines.
plus, it would make the game more realistic.