Mergers are always a tricky business, and for an insurance industry with excess capital available, they're likely on the agenda for the coming year. Before giving in to the urge to merge, several major industry executives cautioned at the World Insurance Forum, it's crucial to make sure that the interests of both merging companies are aligned.

According to Brian Duperreault, president and CEO at Marsh & McLennan (MMC), "You are always going to run into problems during a merger so you need to make sure your interests are aligned. If you are divided when you start you will be still be divided at the end. Aligned management interest is what makes for a successful acquisition."

AP reports that Liberty Mutual, the nation's largest provider of workers' compensation insurance and its sixth largest property-casualty insurer, is buying Safeco (NYSE: SAF) for $6.1 billion, a 51% premium over Tuesday's close.

Having spent years working for Liberty Mutual in the 1990s -- part of it for Gary Gregg, who heads the Agency Markets unit that will manage Safeco -- I know that this deal may well be the largest in its history. Safeco sells $5.9 billion in insurance policies a year, while Liberty booked annual premiums of $20.2 billion. Safeco has posted poor earnings and its stock has tumbled recently. Bloomberg News reports that Safeco's auto unit posted a loss at the end of 2007 because of rising medical claims and repair costs, leading to a 33% decline in fourth-quarter profit and a 19% decline in its stock in 2008 before this morning's announcement.

It looks like there will be more consolidation in the personal lines property casualty industry. Seventy one percent of analysts tracking insurers of homes, cars and businesses expect a "significant increase" in mergers in 2008, according to an Accenture (NYSE: ACN) report based on 108 stock analysts in December and January. Candidates for acquisition could include Progressive Corp. (NYSE: PGR), Mercury General (NYSE: MCY), The Hanover Insurance Group (NYSE: THG), and The Commerce Group (NYSE: CGI).

Peter Cohan is President of Peter S. Cohan & Associates. He also teaches management at Babson College and edits The Cohan Letter. He has no financial interest in the securities mentioned.