“I couldn’t help myself.”

“I couldn’t help myself.” “We were getting worried that it’d be ruined for us,” Mr. Downey Montreal canadienssaid. “But now that we can watch the simulcast, we won’t have to avoid Twitter, or the Internet in general, at all this time.”

Given that “Lost” has stretched on for 121 episodes over six seasons, each more enigmatic than the last, its die-hard fans feel they have a lot at stake.

“If you’ve invested that much time watching the arc of the show, you don’t want to have it blown,” said Christopher Frankonis, 40, who works at a bookstore in Portland. “You want the payoff to be as pure as possible. You just have to log off and wait your turn.”

The tension between the oversharers and those who just don’t want to know has at times pitted friend against friend.

“If I post about ‘Lost,’ I try to keep it cryptic,” said Kristina Lucarelli, 23, who lives in Manhattan and was watching the show this week with friends and about 150 other fans at an East Village bar called Professor Thom’s.

But two weeks ago, after watching in disbelief as (spoiler alert) two of the show’s main characters met a watery demise, Ms. Lucarelli quickly posted about it. “I was so shocked,” she said. “I couldn’t help myself.”

“She completely ruined it for me,” interjected Whitney Jefferson, 25. “I was waiting to watch it with my boyfriend and she tweeted about it and then commented on Facebook.”

Analysts say Twitter is typically a benefit to time-delayed television. “The East Coast builds the West Coast’s awareness,” said Mark Ghuneim, chief executive of Wiredset, a digital advertising agencyMontreal canadiens based in New York that creates and tracks social media marketing campaigns. “People see others talking about it and they tune in.”