Is tea that has been out on air for long dangerous to drink? Suppose you made a cup of tea (the real tea, not bagged, and not a fruit drink) with no additions, but you forgot about it while doing other things (house stuff, homework, your job) and it has now been 2 hours since you made it. The tea is cold, possibly bitter, and a significant portion of its flavor is gone (this has been the usual result for me with all real teas). It's not so good any more, but is it safe to drink now?

As the saying goes, a cup of tea left overnight is poison. How true is that in terms of actual hazards?
As long as you haven't added something that will dramatically increase the spoilage time (milk, or sugar), it should follow roughly the same rules as coffee. Most citations I've seen say the taste begins to go off at around 8 hours, which is a good indicator of spoilage. It's going to taste yucky if you forget and leave the teabag in it as well, but that's just over-steeping.