Regarding reddit and PR. A little hard to explain. Needless to say, there is a high probability that institutions will readily respond to negative or positive feedback fostering in the reddit ecosystem.
Regarding visiting steam. The slowdown seems to have only affected the distribution end of steam. All other services seem to work as expected.
Regarding toning down deals. Not sure what you are asking, but methinks L4D is a lot more popular that expected or perhaps they did anticipate the rush and was testing the load.