I manage lots of WordPress.org installations for different clients. Typically they do not manage the posts or pages themselves, preferring to stay out of things and let me do it.
JetPack functionality is great, but obviously you need to sign into a WordPress.com account within the installation to access it.
My question is – is it recommended to create new WordPress.com accounts for each client, or shall I just sign in to mine on each installation? What are the pros / cons e.g. are the WP-stats merged (this would obviously be bad)?
Many thanks
Nope, you only need it to activate. I use it on 4 sites with same account.
You only need one account, however I often create a new account for client work. WordPress.com allow accounts without blogs on WP.com which is normally what I do if someone else may possibly need access to the account.