1) Exactly. This doesn't help at all with server-side rendering of times, which is usually the use-case (times associated with forum comments, etc.). IP address detection is pretty annoying to do (and doesn't help with VPN's etc.), but a quick <script> in the <head> of any page that does an instant "redirect" to put the JavaScript timezone info into a server-side session variable is a functional, albeit hackish, solution. (If you don't have JavaScript enabled, then just serve up UTC times, it's an edge case.)
2) Usually your times are stored server-side in UTC, so you never have to worry about timezones anywhere. It simplifies things a great deal. "Naked" = UTC. You assume that, whenever it's stored, it's already been translated from the user's timezone when the date was initially generated, or else the time it happened on the server was the actual time.
Sorry, I meant naked date/times that are displayed on a page. It might be that site A gets the user's local time zone correct, but site B, C, and D don't. By displaying the time zone abbreviation next to the displayed time it removes all ambiguity and possibility for error. Also, if it's a time zone abbreviation that's displayed (e.g. EDT) make sure to mark this up properly and fully explain which time zone and country this is for. I can't remember which, but there are some time zones that have the same initialisms. Some don't have initialisms at all, and users from, say, Poland might not know what PDT is either.
This is what we did on a recent project. The times were left at UTC with a hover tooltip (JS with a fallback to title="Coordinated Universal Time") and we used the "timeago" plugin for jQuery http://timeago.yarp.com .
2) Usually your times are stored server-side in UTC, so you never have to worry about timezones anywhere. It simplifies things a great deal. "Naked" = UTC. You assume that, whenever it's stored, it's already been translated from the user's timezone when the date was initially generated, or else the time it happened on the server was the actual time.