Drug maker Shire has announced it will buy ViroPharma for $4.2 billion. This comes on the heels of Amgen's $10.4 billion offer for Onyx Pharmaceuticals in August and Perrigo's acquisition of Elan Corp. in July for $8.6 billion. Those are just a few of the dozens of pharma deals this year that have enriched shareholders. The good news? This is only the beginning.