A. Never.

Why they don't change it to a once every three years event (or two years, or four years) I'll never know.
Anyway, for the record....
Roger Federer Disappoints Tennis Fans with Davis Cup Withdrawal
This happens every single year, but every year it leaves a bad taste in the mouth of tennis fans. Roger Federer has again decided to pull out of a first round Davis Cup clash.
From 2005 to 2009, Federer has skipped the first round every year only to come back and be the hero every September as he saves the Swiss team from relegation. He's only played 12 Davis Cup matches since 2005.