As large companies mature they move from doing just talent acquisitions to doing talent and tech acquisitions to eventually doing all three types of acquisitions. Usually it takes a startup beating the large company in an important area for the large company to realize the necessity of business acquisitions. For example, Google seemed to dramatically change its attitude when YouTube crushed Google Video. Eventually every large company has a moment like this.
Read more about these types of acquisition on Chris's blog.
Update: Another type of acquisition, via Seth Godin.
