The Blam Threshold is usually used to refer to the score a summission has to be at or above in the final moment of Judgment to stay on the Flash Portal. Before the 2007 re@@@ this was the score of 1.6 after a certain amount of time on the Portal. Since that time, it is after 200 votes, regardless of how much time it has been on the Portal.
Above and below the Threshold
On the Newgrounds 0 to 5 voting scale, voting 0 or 1, is a blam-worthy score, effectively means that the voter is denying a submission's right to exist on Newgrounds. A vote from 2 to 5, in contrast, signifies that a user is at very least willing to tolerate a piece of content on the Portal. A score of 1.6 signifies that a submission's reception is at least a little more positive than negative.
The significance of the figure 1.6
Since the score of 1 is defined by Newgrounds as "This makes poop look good", and "Nothing too new or interesting", and the Blam Threshold is between those two, it is clear that Newgrounds envisiges accepting fairly poor submissions onto the Portal.
It is known that many voters actually only vote either 0 or 5, with a perception that either a submission is good and they want to Protect it as much as possible, or bad and they want to push it towards Blamming. Since the half-way mark between the 0 and 5 is 3, it is much easier to Protect a movie than to Blam it.