There are two issues here. First, it's letting you know that you have instances available to you eventually. The other alternative is for players not to be able to see any instances until they have access to them, which doesn't provide much incentive for them level up. If you know "in just one more level" you can hit up Stockades... well, that "one more level" is going to seem more important to you than it really is, and get you to play the game for that extra hour or so. At the end of the day, that's a good way for Blizzard to make more money.
Secondly, there is a bug where the dungeon finder tool is not allowing players of certain levels to queue for level appropriate dungeons. This could be what you're experiencing, however I can't be sure.
Either way, don't worry about it too much and just level up a bit. You'll be happier all around.
Gamer am I asked...
"As someone who can't raid, I would still really like to see how the Lich King saga ends. Will WoW.com do a spoiler filled post about the end of that saga once we know how it ends?"
"How many wow.com writers actually read the comments in their articles?"
Everyone reads the comments, and the editors regularly moderate. We don't comment all the time, and we don't normally respond to trolls or spitefulness. But we're here.
Nizari also asked...
"I remember there was a period during TBC when server maintenances would just be rolling restarts, and long down times were rare. However, for pretty much all of Wrath, every Tuesday is at least 6 hours of downtime. Is there something about Wrath that requires more maintenance? "
There have been times in the game where maintenance didn't happen as regularly as it does now. But those are only isolated pockets. Realm maintenance fixes a lot of things and increases server stability substantially. In the ideal world all that would be required each week would be a realm restart, however with a game as large and complex as WoW, that's not in the realm of possibilities.
The other important thing to remember is that game changes are coming much faster now than they did at any other time in WoW's five year history. This means that more minor patches to the servers are needed, and those often happen during weekly maintenance.
And I hope in bringing up this topic that no one decides to starting QQing over other games not needing restarts or maintenance periods. Other games have their servers go down, and no other games have as many people playing on their servers as WoW does. Such QQ is just a myth that gets thrown around a lot when talking about WoW's servers, so let's just dispel the myth right away.
Have questions about the World of Warcraft? The WoW.com crew is here with The Queue, our daily Q&A column! Leave your questions in the comments and we'll do our best to answer 'em!