ReadWriteEnterprise is reporting, via Jakob Nielsen's annual report, that Intranets, "are becoming a higher priority for organizations. Intranet
teams are growing in size, and the best of them are embracing new
trends such as mobile accessibility and social networking."

Unfortunately there is no mention of security. These intranet applications like SharePoint are not well protected by traditional firewalls. You need to look to "next generation" firewalls, as defined by Gartner, Forrester, and others.

Update: The Gartner link above will only work for Gartner customers unless you want to pay for the report. Fortunately, Palo Alto Networks, a next generation firewall vendor, has posted the full Gartner next generation firewall report.