Our use of plan9 was really incidental and was in support of our work on Akaros. It was a tool we used to support our development environment, but not a focus of development itself nor something we did development on directly. We did contribute a few things back to 9legacy; some bug fixes for the i218 driver where the NIC would lock up come to mind; we found a few bugs in the 9pi USB stack that Richard fixed. I suppose that counts as "improving" plan9.
Work on Akaros has stopped however, at least at Google.
Those that I know who use acme at Google are not, generally, writing web services. Rather, they are working on the Go compiler and runtime. I suppose it's possible that someone uses acme to write web services, but the number of people doing that kind of thing is actually pretty small, even though a lot of people think of Google as a "web" company. I dunno; I work on kernels.
- Dan C.