This has been a LONG standing debate in numerous venues, and will probably continue to be forever. I've been streaming feeds for years and have not had an issue. Simply put, I think when your stream is "scanning" that departments really can't gripe about it too much, as you are not providing an "exclusive" feed for their department. If you provide a feed streaming one particular channel of a department, they may or may not take issue with it. I know that Connecticut State Police has made it abundantly clear that they do not want their transmissions fed over the internet.
I haven't done this yet, but it might be a good idea to provide an "open letter" at your website or feed host's site to any departments that your feed covers, providing them with the opportunity to e-mail you to request that their channels be removed from the feed. It's better to work with them than against them.
I think there is also an onus on feed providers to act with common sense. Do not include frequencies or talkgroups that are used for covert/tactical/surveillance type of operations. Sure, they're neat to listen to, but consider that you may be compromising the safety of the public safety officials involved. The argument "well, they should be using scrambling or encryption for that type of stuff" is lame; I work in the public safety field and trust me, the coffers are not bottomless. Equipment costs $$, and not all departments have $$. Treat them with respect and openness, and our feeds will continue to stream merrily into the future.