PaulMurrayCbr:
The law of assignment: any poster desperately needing immediate help is invariably a student with a deadline.
Here are some corollaries to that Law:
Division of Response: some will help with what they know, some will ask questions, some will pose alternate puzzles that that lead to the solution, and some will not respond.
Continuity of Guidance: I have observed that when when one 'guru' is helping a supplicant - who is actually learning - other gurus hang back unless something important must be added.
Help Shopping: Most supplicants with a single post will not return, no matter how many replies are given.