Andrew,
Yes, you can limit the maximum order amount per order. On the Admin Menu, under Manage products, select the product to edit and in the "maximum order quantity" box enter the maximum number of units allowed to purchase that product. If the user clicks add to cart with a quantity greater than the max order quantity then the cart will display the message “Product XYZ” has a maximum order qty of X units” and will not allow the product to be added to the cart until the user enters a qty that meets the maximum order quantity threshold.
Kevin