According to the report, two manufacturers that are currently willing to work with Google on this are Motorola and LG. Samsung and HTC are apparently not
interested in the Silver Certification program at this point. LG has manufactured the last two Nexus handsets, while Motorola was owned by Google until recently. It probably is not a coincidence that TouchWiz and Sense, the UI skins that run over Android on Samsung and HTC's handsets respectively, are among the most well-known manufacturer UIs for the Android platform.
The Nexus One (built by HTC) was the first phone in the Nexus series. Coming right after the amazing success of the Motorola DROID, it was the first Android handset to offer Android 2.1. The Nexus range became known for the Google Experience, stock Android and quick updates. If the Silver Certification does go through, Google might leave stock Android to the Google Play edition handsets.
source: TheInformation (SubscriptionReqd) via Gizmodo