It seems like a strategic acquisition. LinkedIn looks poised to be expanding more into business operations/communications, especially given their previous acquisition of CardMunch. I can definitely see them trying to position themselves as an indispensable communication tool for industry and business professionals.
I think Yammer is probably too expensive at this point. But they might want to build a competitor. Social CRM in general is a hot space and LinkedIn is well positioned to take a big chunk of that market.
