A thoughtful book on the consulting industry, Business Consulting, by Gilbert Toppin and Fiona Czerniawaska, introduces this buzzword to describe the situation where “some clienta are encouraging consortia of [consulting] firms to work together on a more equitable basis, with their own staff taking on the central coordination role.” (pg. 168). Interesting, but not apposite for law firms.
Coordinating counsel, such as one firm to ride herd on hundreds of similar drug cases around the country, often using local counsel, would be a cousin of multi-sourcing. True multi-sourcing, however, would be equal firms paired to achieve an end, such as a good litigation firm teamed as an equal with a good IP boutique in a patent infringement case or a Delaware corporate firm teamed with a securities law specialist firm for a hostile takeover. Multi-sourcing of law firms hasn’t surfaced much, to my knowledge. (Although I suppose huge problems bring in slews of firms, think Exxon Valdez; the key idea of multi-sourcing seems to be, however, that the firms work closely together.)