As for the cyclical growth, I can see a lull for a day or two as people try to cash in a bit on the big spike, but more than a few days suggests to me that the threat of gov't action is more of an issue than you suggest, especially when the numbers of people learning about Bitcoin is surely following an exponential curve. The more veteran Bitcoin users can dismiss this threat more readily, I think, but the newer bitcoin users are those that are less and less knowledgeable on cyptocurrency economics, and would thus be more fearful of gov't action. If it is merely a technical lull, it would have to jump by 10 dollars or more in the next few days.
And to the last two posters: The government can't do anything to Bitcoin itself, but by making it illegal, it prevents the growth of bitcoin into the mainstream. Forget buying anything on Amazon while this government ban lasts.
We've had lulls that lasted for months. A couple days is meaningless.