Thomas Weisel and other heavyweight bankers and investors from the dot-com heyday are now assessing opportunities among the social media start-ups.
SAN FRANCISCO — Thomas Weisel doesn’t have much personal experience with social media. He has never opened a Facebook or Twitter account, and he has resisted buying an iPhone.But Mr. Weisel knows a lot about overheated markets. His firm, Thomas Weisel Partners Group, was a dominant force in taking technology companies public during the dot-com boom and was hobbled when that bubble burst in 2000.











