As blocksizes are not infinite we need a step limit for transitive transactions if we want them to fit in the same block.
I made a small investigation into what is a good maximum number of steps. But this also led me to investigate the amount of CRC that can be transferred to a remote node in the trust graph, in a single transaction. It includes an analysis of how many steps are needed for different amounts of circles.
You can read about it in the circles hand book:
It has beautiful diagrams 
It turns out the pathfinding used in the circles-api performs quite bad in terms of reaching a large number of steps fast for remote transactions.
We in the circles dev team are currently working on a new pathfinding services with more accurate trust indexing in a new repo called “slimemold” (named so after this organism’s ability to find paths)