Many companies would find similar behavior among their employees to be unethical and cause for termination.

For instance, large retailers have strict gift rules in place so that suppliers cannot "bribe" the retail buyers to get their stuff on shelves.

Our Walmart contact in their technology center wouldn't accept a cup of coffee during a site visit, without putting a quarter on the table. They Strictly enforce a ban on gifts and favors, calling it all bribery and grounds for getting fired.

But those are instances where there is no precedent for tipping.