said by Teddy Boom:
The practical question is, do some employers require certain ISPs in written agreements, or use technical means to blacklist some ISPs. It may not be warranted, but it might still happen.
For the first part, "not that I've heard before," but you never know. For the 2nd part "I've seen wierder."
Just had a recent issue with a client they "just found out" they were blocking a /15 netblock from a certain
major Americas ISP for the last 9+ years... and d**ned if anyone knew why it was in there.
It takes all kinds.