lol no.
I feel absolutely no guilt or "bad feelings" what so ever.
Perhaps if nintendo was a strugling company and the ds was the last hurrah I'd feel guilty but the DS prints money.
And they make a profit off the hardware so they still made some money from me.
...I'm sorry to tell you this....
Of course they're used online, there are people who like to win mo matter what, it's not their fault they suck at games.
Just always play with friends/trusted people.