GigaOm's Barb Darrow reports on Netflix's latest open sourcing of its middle tier load balancer.

According to the blog:

In AWS cloud, because of its inherent nature, servers come and go. Unlike the traditional load balancers which work with servers with well known IP addresses and host names, in AWS load balancing requires much more sophistication in registering and de-registering servers with the load balancer on the fly. Since AWS does not yet provide a middle tier load balancer, Eureka fills a big gap in that area.

The consistency of Netflix open sourcing its infrastructure makes it a pattern. And, to understand the a pattern you need to ask what problems is Netflix trying to solve. Why is Netflix sharing its infrastructure?

The process of open sourcing the code gets the developers to clean up their code and document. There is some bad open source code out there, but there is also some very good. The Netflix team takes pride in their sharing, so they want it to look good.
Sharing this infrastructure makes Netflix an active member of the open source community.
The open source community then comments and makes input on Netflix contributions which are resources not paid for.
The above makes the developers feel good about their participation in solving plumbing type (fundamental infrastructure) of problems that are not critical for protecting their IP.
The above allows Netflix to recruit new people. Note almost every one of these postings ends with sentence, and we are hiring more people. Finding really good people is a priority for Netflix.
Netflix gets positive PR consistently at conferences as they get mentioned for sharing and innovating in their IT infrastructure.

There are probably many more, but you get the basic idea.