Social contacts platform Plaxo is adding two new stream aggregation features to its stream service Pulse. Pulse, which tries to build a social network around third-party data, allows users to stay connected to their friends’ updates (using oAuth, the secure data portability standard), via a feed, across different social networks and platforms. Plaxo is now adding a “Comments-in-the-Stream” application, similar to the Facebook comments feature, which allows users to comment on what friends are doing on other networks and platforms.

Plaxo is also integrating Pulse with travel itinerary site TripIt (via their open source API), injecting itineraries into the calendar option and giving users the ability to share travel plans with their Plaxo connections (you can specify who you’d like to share the itinerary with). Contacts will see your trips in their Pulse stream, which will include images and destination specifics. You will also be able to see your travel plans in your own stream and calendar, with a link to the full itinerary on TripIt.com.

Plaxo, who was bought by Comcast last year for $150 million, had trouble pulling Facebook contacts into the Pulse stream. The company recently partnered with Google to release a hybrid protocol that combines OpenID, the open online identity standard, with OAuth, to transfer contacts from one site to another. Of course, this protocol rivals Facebook Connect, but that’s just for Facebook apps.

It seems that there is a trend emerging regarding social networks adopting each other’s features, like Plaxo did with its Facebook-like commenting feature. Today, Facebook unveiled it new real-time update feature, which takes a page out of Twitter’s book. And Google Reader drew inspiration from FriendFeed when giving users the ability to comment on items that have been shared by their friends.