One of the recent speakers was Kent Collier, CEO of Reorg (https://www.crunchbase.com/organization/reorg-research#secti...), an information service to the buy-side that focuses on arcane and opaque information, particularly bankruptcy. They are a smash hit that only took $1.3M in financing that now does $1M a week in revenues.
His view is that solo founders and preferable. The reason he gave was that it takes such a clear and unambiguous vision, with total dedication to that vision, that any space between multiple founders creates drag and can kill the startup.