1. What should the default be? Java build systems default to building dynamically linked, though it's a few lines to change. IMO dynamic is a better default for large projects, as you usually have more library modules than executable modules. On the other hand a large project is likely to already involve a fair bit of build config, so maybe the defaults should be optimized for small projects.
2. Whether you allow dynamic at all. To my mind it's always worth having the option, and I think Go will come to regret not having it if and when it ever gets used for large projects.
There are plenty of large projects like kubernetes/docker/rkt/influxdb/tidb/cockroachdb and so on. Go is providing quite large memory efficiency and sub-millisec GC as compared to Java.
As of Go 1.8 it also provide plugin support though I am not sure if they are any where near Java in term of dynamic libraries loading support.