With advances there is the risk that some implementation will be left behind, and if there is not an active developer community become orphaned.
There are two significant areas of risk:
* lack of support for new features - while an implementation may still function as part of the federation, some aspect may perform sub-optimally. *A current example, with the ruby server, is sitemap.json being created on demand rather than keeping an up to date version available.*
* lack of bug fixes
The ruby server falls into this category – it has not been kept up to date with the advances that have been made to the node version of the server.