Can confirm too in 1.5 prerelease, even spawns the nonreactive hostile mobs when in peaceful mode
I added dummy objectives, sorry for not including that. It just comes to my mind that i also used the same displayName for around 15 of the objectives, since i needed different values for each players at once in one category.
An example "scoreboard objectives add s11 dummy Skill" with just the actual name varying from entry to entry.
When i reproduced the situation again, i noticed that the RAM usage of java didn't increase but the fps decreased anyway.
It is still occuring for me too in 14w31a.