Since there was a healthy amount of discussion on this topic during today's Office Hours call, I ifgured I'd continue the discussion.
In effort to share work and not just ideas ill detail how we are currently setup. Today the CSM is responsible for all renewals and expansion. Depending on the product/service they are trying to promote they will leverage a sales executive to come help with demo and sales cycle. I joined my current company to first help with renewals and build a more repeatable process and second to then build out account management (with CS department).
I do not think there is one right answer on this subject because so much can depend on the complexity of the product being sold, the solution your customers are trying to implement etc... I think we struggle with these questions becasue we're all managing this in phases. Even if you think CSMs shouldn't be managing upsell i doubt you can just hire 10 great Account Managers over night. Meaning CSMs will be resonsible until there is a new team in place etc...
I think its possible (but difficult) for a CSM to stay a "trusted Advisor" while trying to upsell. However i think the greatest issue will be focus and time.
If I'm a CSM and have been tasked with helping 25-50 customers adot a complex solution, AND I've been tasked with an aggressive quota of upsell. The CSM will keep focus on the adoption and fail at the expansion. Likewise, you give an account manager an agressive quota and also tell them to drive significant adoption ... they will fail at one.
Telling a CSM to grow this base by a small % is one thing. but to have an agressive account management campaign takes significant amount of work. A lot of time is needed to prospect and study the true opporutnity within a terrirtory, put together sales pitches and be practiced, manage opportunities and sales cycles, ask for the sale and NOT leave anyone behind....
I also think CSMs have it in them to succeed in either... but when I start looking at the true potential of upsell in our existing user base, and then consider the effort it will take to close even 30% of that potential I'm not sure my CSMs would have the time. Somethin would suffer.
So I think much of this quetsion depends on how agressive are our growth plans? and do you expect someone to acheive these company goals with divided attention. Hopefully this helps fuel some brainstorming