Scrum often works extremely well for small co-located agile teams but fails to when applied to larger more complex projects with distributed resources.
The obvious question is why.
As Agile consultants (Coaches, ScrumMasters, SMEs) we often must assess the teams and organizations to determine what challenges (i.e., scaling factors) may impact the team's performance during the pilot.
While I have a good deal of experience with several large organizational transformations would like to hear from others regarding their experiences to capture a more complete list.
Please post your responses.