In periods of uncertainty, there's a tendency to go back to what you know. That's what has happened in the currency markets in the wake of the terrorist strikes in the US.
As the New York Stock Exchange closed down for four days, market participants around the world sought security in familiar surroundings. Only a tiny proportion of what is in any case a much-reduced deal flow is being done online. In the longer run, though, it looks likely that the possibility of threats to physical exchanges will make online dealing increasingly attractive.
Although price takers certainly appreciate the transparency that online trading has already brought about, after the attacks they were more acutely aware of the other side of the coin. Online platforms aren't good at market detail. There's little an internet portal can tell you about market depth, nor can a screen hooked up to rate engines advise on the timing of a deal.