Don't wish to put anyone off from using this airline but if you do decide to fly with them, I would suggest you pay by credit card.
Over here bets are being taken for the next Airline to go bust....odds for British Airways, Virgin Atlantic, Air France & Lufthansa are all at 100/1 but the odds for United Airlines are as low as 20/1
Whilst it is very unlikely that they will be the next airline to go bust they are doing themselves no favours by this 2nd checked bag fee. It might put off more passengers from using this airline in favour of an airline without such a high extra charge.
I will be looking for an internal flight a bit later this year as I have a cruise planned & this extra charge makes me less likely to use United. The money saved could pay for my taxi fares.