There are good reasons to be skeptical of the FIDE Blitz ratings:
1. Players play only a few sessions of rated Blitz each year. Even some Blitz tiebreaks in otherwise rated tournaments aren't FIDE rated.
2. Blitz games have much more volatility than longer time control games. A better Blitz player will still come out on top if they play enough games, but there are fewer draws and upsets seem much more common. A few dozen games a year is probably not enough to sift out the better players from the noise.
3. Probably because there are so few rated Blitz games, FIDE decided to double everyone's K factor for Blitz and Rapid ratings. If you beat someone your rating in Classical chess gets you +5 points, but in Blitz/Rapid you get +10 points. This makes the Blitz results even more volatile. Since each shorter Blitz game tells you less about a player's skill, it makes more sense to me to halve the K factor rather than double it.
Just take a look at the huge point swings from this year's 21 game Blitz Championship: http://2700chess.com/blitz While some of this reflects players approaching their true rating, I'd wager a lot of it is just noise. (ex. Kasimdzhanov gained 98 points for a solid 2810 performance, Vovk gained 145 points for a 2827 performance. This rating change was gained over ~3 hours of total playing time, less than a single classical game! They came in 9th and 10th place.)
1. Players play only a few sessions of rated Blitz each year. Even some Blitz tiebreaks in otherwise rated tournaments aren't FIDE rated.
2. Blitz games have much more volatility than longer time control games. A better Blitz player will still come out on top if they play enough games, but there are fewer draws and upsets seem much more common. A few dozen games a year is probably not enough to sift out the better players from the noise.
3. Probably because there are so few rated Blitz games, FIDE decided to double everyone's K factor for Blitz and Rapid ratings. If you beat someone your rating in Classical chess gets you +5 points, but in Blitz/Rapid you get +10 points. This makes the Blitz results even more volatile. Since each shorter Blitz game tells you less about a player's skill, it makes more sense to me to halve the K factor rather than double it.
Just take a look at the huge point swings from this year's 21 game Blitz Championship: http://2700chess.com/blitz While some of this reflects players approaching their true rating, I'd wager a lot of it is just noise. (ex. Kasimdzhanov gained 98 points for a solid 2810 performance, Vovk gained 145 points for a 2827 performance. This rating change was gained over ~3 hours of total playing time, less than a single classical game! They came in 9th and 10th place.)