Sorry if my post did not sound serious, but ... Yes!
Ok, if you're serious...
Interestingly, a speederbike could not take out another speederbike since it has personal scale weapons and vehicle hull points.
Personal scale weapons need to score 10 points of damage to inflict 1 point of Hull Trauma.
Since a speederbike has no armor, and a VERY low Hull Trauma Threshold it's actually quite easy for personal scaled weapons (like blaster rifles and up) to knock out a speederbike in a few hits. Auto fire weapons can even one-shot if the roll is hot enough.
Does speed come into play? It seems that it should.
That's exactly the sort of thinking the setback dice are for. Otherwise to-hit is determined as usual for the shooter.
So how to target a person in an open topped vehicle, the use of Triumphs, or the application of shooting equipped items as Krieger said, are the two simplest solutions. Though generally there's not going to be any huge advantage to targeting the rider over the bike.
Edited by Ghostofman, 17 March 2014 - 09:11 AM.