Don't think it is a simple yes or not answer there. I think first it depeds on the expectations of the team. A top team like Tampa, deep and skilled, you would expect them to go deeper in the playoffs. That bar gets set right or wrong for the team and what is felt they should accomplish. It is very different for a team just squeaking into the playoffs too. Then there is the match up for the round. Is it a team seen as weaker, a david vs goliath, or a slugfest up for grabs for who wants it most?
In the case of Tampa vs CBJ, Tampa had HUGE expectations for a very strong and deep team. That bar was set and the match up appeared to be lopsided, but nobody really looked at CBJ.
CBJ came in with an all or nothing we are going for it attitude. Sometimes the most dangerous teams are the one's everyone didn't expect to be there, and one's that get written off as done. They have nothing to lose! CBJ had a good team but not a lot of depth, but then went and added bigtime to their top end talent. Nobody really acknowledged that.
Tampa went in overconfident, thinking hey we just keep rolling along. They found themselves in an absolute fight and were unprepared and could never get themselves righted when they discovered this was not going to be the easy series everyone said it was, it wasn't the lopsided series.
Sometimes it is that, other times injuries take a heavy toll, sometimes it is a bad bounce aka Smith with the old Oilers
.... any number of things can cause upsets.
It is always disheartening. Fans and media like to overreact, more so now that there is a platform where they can get vocal, put up videos of burning jerseys etc etc. Everyone forgets the players don't play to lose, they play to win, and no one is going to be more dissapointed than they are. The real question is how the teams who got punted in Tampa and Pittsburgh now respond and come back from it. It can crush them, or they can learn and rise above and it fuels them. Time will tell there.