Let your users bring LinkedIn profiles and networks with them to your site or application. You gain better awareness of your users, increase productive engagement, and gain reach through the 52 million professionals on LinkedIn.
(LinkedIn.com)

The Gnip API provides notification of activities (events) occurring in a variety of services and, whenever possible, a guid that identifies the activity itself vis a vis the service it was created on. Activity examples include a user “tweet” (twitter), a user “dugg” (digg), a user creating a blog post, etc.

(see gnipcentral.com, Gnip API)

You can leave your polling tasks to Gnip and only consume the data over their API.