As of Minecraft 14w04a and above, it is no longer possible to use "/setblock" to spawn the technical block "minecraft:lit_redstone_lamp" (formerly Block ID 124) into the world. Instead, the default (inactive) "Redstone Lamp" spawns.

The following versions allowed the spawning of active Redstone Lamps:
13w38c, 13w39a, 13w39b, 13w41a, 13w41b, 13w42a, 13w42b, 13w43a, 1.7, 1.7.1, 1.7.2, 13w47e, 13w48b, 13w49a, 1.7.3, 1.7.4, 14w02c, and 14w03b.

The syntax used is:
"/setblock ~ ~2 ~ minecraft:lit_redstone_lamp 0 replace"

Intended behavior:
The Active Redstone Lamp should spawn into the world using the "/setblock" command, and then become an "inactive" Redstone Lamp, provided the Command is not repeatedly executed via a Redstone Clock.

Additional notes:

It is still possible to use the "FallingSand" TileID of 124 to replicate the above intended effect, as in the following syntax:

"/summon FallingSand ~ ~2.5 ~ {TileID:124,Time:1000,TileEntityData:{}}"

Alternately you can also use this syntax, and the block will become intangible:

"/summon FallingSand ~ ~2.5 ~

"

The following YouTube video shows both the intended behavior, as well as the bug in action:
http://www.youtube.com/watch?v=Wns5BFO-wGA

Also included are a screenshot of the "Active Redstone Lamp" working, in 1.7.4, as well as a screenshot of it no longer working in the 14w05a snapshot.