I do not think it makes sense to treat a market as likely Invalid based on an unmatched bid for 10 shares at any price.
Requiring a larger bid size is one possibility.
I'm not sure that requiring a trade to go through will help as people can trade with themselves and manipulate it so that markets that they didn't start are seen as Invalid (to collect fees in a market they started).
I do not think it makes sense to treat a market as likely Invalid based on an unmatched bid for 10 shares at any price.
Requiring a larger bid size is one possibility.
I'm not sure that requiring a trade to go through will help as people can trade with themselves and manipulate it so that markets that they didn't start are seen as Invalid (to collect fees in a market they started).