Earlier this year, two Citibank customers sued the financial institution on the grounds that it used unfair and deceptive trade practices by not fully disclosing that frequent flyer rewards offered as a incentive for opening a checking account could be taxed. The promotion, which amounted to as much as 40,000 miles, ended up costing the pair an estimated $350. Citi said that its rewards program clearly states that the bank may send a miscellaneous income tax form to participants for the acquisition of points. So while Citi may be....