I am not aware on any rules preventing a too high number of entries at a limit price. Nevertheless you usually have controls for each trader id. A trader cannot have too many orders in the book or send them at a too high frequency.
[EDIT] Moreover, on most trading platforms you cannot have orders too far away from the mid (or a reference price like the previous close). See for instance the 2014Q4 convergex traders guide p4
Hong Kong, for instance, will reject a limit order that is more than 24 ticks away from the current bid or offer. During its pre-opening period, Tel Aviv will not allow a limit order that is more than 35% from the previous day's closing price. In the US, NYSE Arca uses percentage price checks:
• If the price is USD 0.01-25.00, your order must be within 10% of the price.
• If the price is USD 25.01-50.00, your order must be within 5% of the price.
• If the price is higher than USD 50.00, your order must be within 3% of the price.
It more or less controls the number of orders in the book.