There are a lot of exchanges now and one exchanges going down cant affect the price of bitcoin its only an exchange, if it were like a few years ago like mt gox it would tell a different story, if one exchange does down then go to other sites.
it absolutely can. each bitcoin currency pairing has a leader and if that goes down confidence takes a huge knock.
gox was catastrophic but by the time it was dead it had almost no market share. it lost its lead months before. it was the amount of historic money caught up in there that hurt.
it's definitely more spread out than in the past but everything's about confidence and that can disappear quickly.