Having limit on number of issues(story,feature ) a developer can work at a time is very effective for agile development . It forces developer not to exceed limit.Suppose we have issue states like – Backlog,Ready,Progress,Code review,Deployment – then a particular developer can have just 2(whatever is the limit ) stories(issues) against her name in state “Progress”.If she is stuck with issue and she wants to take a new issue in between then she has to drag back at-least one issue to ‘Ready’ state. This is good as other developers can find this issue interesting and can work on that .
Lets take a case of Jira a great extensible tool for issue tracking and agile development through Green hopper.We have kanban board setup there and we had setup a WIP limit through our in house developed plugin – while transition to ‘Progress’ state , plugin validates that developer is not crossing that “WORK IN PROGRESS” limit.
Wip limit gives very clear picture that who is working on what.
If interested to use that plugin let me know.