So Sunama... would you trust Piquet to have the skill to brake test you enough to slow you down without causing an accident?
If I was following Piquet, closely, in a BrawnGP car which is much faster than his Renault, I would try and drive as closely as possible. However, the moment he brake tests me the 2nd time (I would assume that the first brake-test was just a mistake or his foot slipped, while the 2nd time would have been intentional), I will definitely back off and wait for the particular corner that I am certain I can overtake him. At some point I'd have to take the risk.
On the other hand, if he didnt brake test me, I would ride as close to car as possible and wait for an opportunity to present itself.
The difference between the 2 scenarios above is that, with the brake testing scenario, Piquet is much more likely to keep me behind him than if he wasnt brake-testing.
Had Piquet brake-tested Barrichello a few times, I'm sure Barrichello wouldnt have been able to overtake Piquet in the way he did, as he would've been a little scared. After the race Barrichello would complain, but by then, the race is over.
I just find it strange that when Senna brake-tests, its all swept under the carpet, but when another driver proposes its use, everyone is calling for bans for dangerous driving. Sorry gents, but brake-testing is a fantastic skill to have if you are an F1 driver fighting for points/race wins/drivers' titles.
I guess its similar to "diving" in football. It is very much a skill that top players have - diving in order to be awarded penalties/free kicks, from which goals can be scored and games won. You may not like it, but it is definitely a skill.