Then there are those you know solely in a professional context. These include colleagues, industry acquaintances, customers, allies, business advisors, and service providers like your accountant or lawyer. You email these folks from your work address, and maybe not your personal Yahoo or Gmail account. Shared business goals and professional interests bring you together. Online, LinkedIn is where you connect with these trusted colleagues and valued acquaintances whom you recommend for jobs, collaborate with on professional projects, and tap for industry advice.