TheoOdo said:

We may agree that it's silly for Obi-Wan to be dressed as a Jedi whilst in hiding, but it's been established - from Return of the Jedi on, if not earlier - that that's just what he was doing.

It's not completely established. Two of those guys lived on Tatooine, so we might expect they were just wearing traditional Tatooine clothing, like Owen. Yoda was essentially a monk wearing sackcloth.

That said, all Jedi wearing brown robes doesn't bother me. It's obviously intended to match the simple robes of a peasant/farmer like Owen. Obi-Wan would just blend in as another farmer.

Now I don't think Jedi should wear brown robes all the time. It seems a very foolish thing to do in the heat of battle. How about some armor? How about a military uniform?

Basically, the brown robes should just be their everyday clothing that they wear while meditating, teaching, and meeting. But when they go on official Republic business, they put on their uniforms. (Perhaps like Luke's black uniform?) For battle they add armor.