TechNet is technically for evaluation only.
MSDN *can* be used for "production" (if that's development and testing) (and if you get the MSDN level that includes Office, you do get one unrestricted Office license that you can use for production for whatever purpose), which is why MSDN is more expensive (MSDN's lowest level is more expensive than TN while offering fewer software).
The problem here is that TN and MSDN are per-user only. You can't get a single MSDN sub and use it for a 5-person dev team: each member of the team needs his/her own MSDN sub. So selling a MSDN key violates the all-keys-must-be-used-by-the-same-person rule.
So if MSFT finds a TN or MSDN key being sold on eBay, it'll kill the sub associated with that key and block all the keys that were generated with that sub. This is why you should NEVER buy a key from eBay without a COA, because the COA is the only guarantee that the key was not generated by a TN/MSDN sub that MSFT will kill once it discovers that it had been abused.