With the debut of the retooled Digg.com last week, Borthwick became one of several executives trying to stage a second act for a once-popular Internet property that lost its luster. The challenge facing Borthwick's team, and other buyers of dying Web brands such as Delicious and Myspace, is to keep those people coming back in an industry dominated by Facebook and Twitter. Other Internet gravediggers include members of the team that founded YouTube, who purchased the link-sharing website Delicious from Yahoo, and Specific Media Inc., a digital-advertising company that brought in actor Justin Timberlake to help turn around Myspace after buying it from News Corp. These deals made headlines last year and attracted plenty of interest, partly because of the nostalgia induced by the familiar names. Digg, founded in 2004, helped pioneer features that let Internet users share news stories with friends. Myspace executives watched in awe recently as photo-sharing app Instagram and other startups quickly shot past the once-dominant social network, said Arvind Puri, who was a vice president at Myspace in 2010 and is now chief technology officer at startup Stayhealthy Inc.