Michael Aiello of Weil, Gotshal & Manges remembers a time, as recently as ten years ago, when some investment banks wouldn’t touch a hostile bid. “They were buddies with corporations, so they didn’t want to launch a hostile bid against them,” he says. But these days—spurred by an uncertain economy, deep corporate cash reserves, and lack of organic growth—going hostile has gone mainstream.

“Everybody does it now,” says Aiello, who represented pharmaceutical giant Sanofi-Aventis in its $18.5 billion hostile bid for biotech firm Genzyme Corporation last year. (Sanofi ended up acquiring Genzyme after upping its bid to $20.1 billion.)