For the investor to flip-yes exchanges is important.
From Devs last update.
'Right now we are hard at work focused on deploying trading so everyone can start moving their BNT around and buying and selling directly from the smart contract.'
They gonna let the apps/smart contract to go live so that people can trade.
At same time people can transfer their BNT to exchanges.
But Bancor is not actively pursuing relationships with them
Guy said previously that exchanges will primarily be useful to serve the non-Ethereum based pairs, such as BTC <-> BNT. And also hinted at them acting as an entry for those not comfortable with wallets etc.
Only buyers who didn't take the time to understand bnt would want exchanges involved. I would like to see no exchange offer it, let the smart contract go live with eth and some other major coins as reserve tokens and let the brilliance of this idea sink in.
There are about 40 million ico tokens (80m total) I expect to see the total bnt to be 200m+ this year easy, you can do the math to figure out what that would do to the value.