I gotta say, I find this question of whether Barack Obama risks getting "overexposed" to be a phony issue. (New York mag's Chris Rovzar offers a pretty solid, straightforward take here.)
A huge part of a president's job is to rally public opinion on whatever vital matter needs addressing (health care reform, tax reform, entitlement reform...). More pressing still, in scary times, he is charged with keeping the public from panicking over major events such as war, natural disaster, and economic meltdown and assuring people that everything is going to be OK. (Because even if there's the real possibility that everything may not turn out OK, a hysterical populace only exacerbates the problem.) To do this, the POTUS needs to talk to the public--and not just the tiny subset of the public who watch Fox News or CNN. Just as important, he needs to be seen--again, by as many people as possible--looking calm, confident, and in command.
Overexposure is what happens to some twitty starlet who winds up on the cover of all the tabloids 10 weeks running for doing little more than changing her underwear (or, just as often, for not wearing any). Obama is the newly minted president confronted with extraordinary crises. People need to see him and hear what he's trying to do to get the country back on track early and often.
Besides, it's way less creepy than having the guy holed up in some secure, undisclosed location ala Cheney.