I?ve never personally been inconvenienced by a protest, so I?m rather neutral about the whole thing. I imagine, though, if I were to be inconvenienced, I?d be pretty pissed off about it, because I?m naturally a selfish person and only care about things that affect me (or will affect me in the future). You might get noticed, but you might also garner even more opposition to your cause from people that are annoyed you fucked up their commute to work/their trip back home to their family.
When you protest, you?re trying to work with the people, not against them. The Michael Brown protestors? All they?re doing is giving the right-wing press more fuel to their argument that these working-class black folk are nothing more than inarticulate savages. ?Cos that?s what they look like. Inarticulate savages. It makes you look less like a campaigner and more like an extremist. (And I?m saying this as a black man myself; albeit, a British one who admittedly was raised in a middle-class household with very little discrimination, despite growing up in a heavily white-dominated city)
Btw, the reason Martin Luther King, Malcom X, and other civil rights campaigners managed to obtain anti-discrimination legislation for America was not because they inconvenienced people and got attention through that. It was because they were consistent with their arguments, were organised, and knew what they wanted to happen. MLK and co. had their brushes with radicalism (Malcom X especially and notoriously), but they got back on the right track and eventually got white Americans to support their side. These Michael Brown protestors are anything but, and are more likely to shout ?RACISM!? than focusing on the non-racial issue of the police being too trigger-happy and not doing their fucking jobs properly. And I?d be saying the same thing about white protesters too.
If they are going to hold up a road or something for their protest, I?d prefer it if I and others were told about it in advance, so we could make plans around it. That way, it?s not an unhappy surprise.