I'm going to play devil's advocate here, and disagree with the norm.
I think that we should allow product recommendations, but only for peripherals (devices that are designed to extend the capabilities of the Raspberry Pi, such as a case/extension board).
We should not allow supplier recommendations (unless there's only one supplier).
My reasoning:
Since the scope of this SE is just one device, the number of peripherals will be limited. This means that answers will stay relevant much longer than other SE sites.
It will be beneficial to provide answers to questions like "Are there any suitable waterproof cases currently available for the Raspberry Pi?". This is more useful than "How do I tell if a case is compatible and waterproof?".
Unlike laptops/cameras, the Raspberry Pi is a unique device with a small following. Some peripherals will be made by obscure tech companies and enthusiasts, which means searching "Raspberry Pi case" will not result in a good listing of compatible cases.
The Raspberry Pi is designed for education, and the people who use this site are likely to range in age, experience and knowledge.
Users may not have the ability to find/research compatible devices - we should help them, and provide product recommendations for their particular problem.
Allowed:
Q: What's the best X for Y?
Q: What devices can I use to achieve X task?
Q: How can I do X? What hardware do I need?
Disallowed:
Q: Where can I buy a X?
Q: My X broke, should I return it?
Q: What's the best USB X? (USB devices aren't exclusive to Raspi)
Q: What's the cheapest X? I live in Y. (Too localised)
Q: What's your favourite X? (subjective)
