The size of the original earnest money deposit will be suggested by the offeror (the buyer)
Mark, THE Realtor who is YOUR listing Realtor, could suggest a minimum earnest money deposit in her / his MLS comments. Those comments would likely have little influence over what the buyer decides to offer. The buyer will likely choose to offer an earnest money deposit that they are comfortable offering and upon the advice of the BUYERS AGENT.
Typically buyers, even on commercial purchases, will offer a very small initial deposit.
If you believe that the initial deposit offered is too low, you can instruct your Realtor to write an increased deposit into the counter offer. The increased deposit (s) can be requested (1) At the the acceptance of the offer. or (2) at some specified date after the escrow period has began such as 7 days after acceptance or (3) at some specified event that occurs during the escrow such as the removal of an inspection contingency.
I don't think you should take the advice of the Trulian's as to the minimum dollar amount that you are willing to accept as earnest money. There are so many factors that enter into that decision, that only you and your listing Realtor should make that decision. - Having made that disclaimer, I can tell you that I represent a buyer client who offered a ten thousand dollar earnest money deposit on a small apartment complex in Sacramento.