When we last visited this question, OCAHO (the administrative office that reviews I-9 fines) found that 30 employees is “small” for the purposes of mitigating I-9 fines.
In a March 1, 2013, decision (MEMF LLC d/b/a Black & Blue Steak & Crab - Buffalo, OCAHO 12A00025), we learn that when deciding if an employer is “small”, ICE should not consider the entire number of people employed in any given year, but the average number employed at any particular time.
MEMF is a restaurant, which is an industry with high turnover. It employed 234 people during the time in question, but only about 75 at any particular time. OCAHO considered this a “small” business for the purpose of mitigating the I-9 fine.