Indeed, as Nicholas pointed out, this happened to many relays!
Using the onionoo database I am calculating the average consensus weight during 18-25 october 2014, and the average consensus weight during 11-18 january 2015 of all relays that exist longer than half a year. Below is the top 20 of relays that dropped the most (so far; the list is still being generated because I didn't want to "DoS" onionoo so I am taking it slow). The full table can be found here: http://nosur.com/consensus.txt
change october january days fingerprint -100.00% 124.32 0.00 283 D542940134156DCA0B872A9AFA43EECDF8E64A50 -100.00% 13549.74 0.00 1119 49095052C6668FB6BB9A2C9CEDB0A79B6193870B -100.00% 16028.09 0.00 275 28F04B33154C6EFF497D793C8E65AF09A7B1427C -100.00% 16740.50 0.00 519 61685F33CB798A87CEA3756CA7649EDB4FD314D4 -100.00% 21390.41 0.00 549 1ECD73B936CB6E6B3CD647CC204F108D9DF2C9F7 -100.00% 34109.42 0.00 209 7C3AE76BB9E9E6E4F2AE9270FD824DF54A944127 -100.00% 41042.60 0.00 327 84F8007D6E33E26EB689E40A65183CBDD5538955 -99.88% 13568.03 16.17 199 7109376DCD7F9A9F707B3138056408F2D786F079 -99.87% 9300.44 12.41 549 1FC841137C1F4C525D869B908E007D1D35727EF2 -99.85% 2446.56 3.64 1829 19D0F028BADD11B79DC5846C1D75497672E85511 -99.80% 9381.42 18.92 439 75DF14AA364152CE23EBF542152BF1B3155A2FD0 -99.68% 31269.41 101.42 189 5AE72C34DAA2EF6A511AF82FAF68AA08BE9802D8 -99.65% 5587.80 19.49 1829 721E494B0E06554D8F9A169BDBF17282C07B2588 -99.62% 1377.67 5.27 215 955AF68665FE0FE26DD79894F9684345CB9FF86F -99.53% 3561.96 16.70 227 CD8C1CF1901ADF4E0C6DA87EE8F2981854423C2A -99.41% 2998.52 17.76 327 27AEFB49809A921119821D4A32F0F3795FD46887 -99.11% 2171.73 19.30 339 24835DBD5492E21F7987DFC3FACB39016BEE59A8 -98.98% 6880.00 70.34 699 D779CB52D412F0DCAA296C9539C4ED03E2DF21A5 -98.96% 1416.23 14.78 259 81E06DAAE3ECB1DD0FFB78EC8A5FE23AB4B13DDB -98.78% 2066.60 25.23 233 C8FB6DB9BE327A05F5B29A2FFC240DACDB3C2967
Almost all of them show the same strong drop end of december and a short spike around january 5th! I wasn't able to find any common features among the relays. It hits both exits and non-exits, fast and slow relays, etc.
Something is definitely wrong here!
Thanks, Bram de Boer