I work at an agency where there is a steady stream of tickets. We are very concious of the cost of task switching. In the case where you are blocked on a task and it is left unfinished in favor of a new task of lower priority, when you finally get an answer on the first task you often have to dro the second task abruptly. So you have two unfinished tasks and all the mind balls you were juggling are dropped on the floor.

However we are also an almost entirely engineering team so there is no resource for getting unblocked that isn't bugging another developer who then drops his mind balls.

It is just the reality of it though, we have tickets and tasks to complete and we can work toward being more efficient, making sure we aren't going to get blocked befor getting started on a ticket and such. It's all a balancing act and it's important to be aware of it, but I no longer get my knickers in a knot over it.