Great question — answering as the UphillTech team:
Maybe the legal point depends on the country you are. But to me, you don't care. It's not a question about is it legal or not, it's a credibility question. If you suggest your visitor to buy something and if this thing is realy bad qualety you will receive bad feedback and bad visibility / seo.
Full answer by Patrick Valibus: https://webmasters.stackexchange.com/a/106998 (CC BY-SA 3.0).
Need it done for your business? UphillTech.
