[shkkmo]

> While it's true that there are U.S. states where it's illegal

Its over 2/3rds of states and includes most major ones have laws against commercial kickbacks. Even in states that aren't you could be charged with fraud under state law.

> Otherwise there's almost no scenario where you can't say "we're friends and they gave me a gift, I chose their company for the contract because I thought they were the best choice."

This argument is silly. It applies equally to federal laws that are frequently used to prosecute kickbacks for government employees, contractors and subcontractors. There are plenty of ways to charge someone with kickbacks besides idiotically labeled receipts.

Just because you think you can get away with something because it is hard to prove, doesn't make that activity legal, let alone moral/ethical.