Enterprise 2.0 will become a $4.6 billion industry by 2013, according to a report by Forrester Research. The top priority for enterprises will be social media applications and tools and most of the money is expected to flow to social networking tools and mashups.

Forrester defines Enterprise 2.0 as the corporate version of Web 2.0. Here’s the research firm’s definition:

In Forrester’s view, the key hallmark of Web 2.0 is efficiency for end users, and the ultimate goal is to use technology like Ajax, rich Internet applications, blogs, wikis, and social networks to foster productive, advantageous behavior among employees, customers, partners, and other networks such as Social Computing, the Information Workplace, and collective intelligence.

Across the board, Web 2.0 tools enter a crowded space full of legacy software and processes that are difficult to displace and with which Web 2.0 software must integrate to be fully effective. Integration with lightweight applications like email and Excel, as well as heavier applications like Web content management suites, campaign management software, portal software, and customer relationship management (CRM) systems, must all be addressed over time.