Not a long while ago I noticed that some had a problem with the DMG tables on skill DCs (see 4E DMG p.42). The DC link level and a suggested DC for Easy, Moderate and Hard checks on each.
This seemed to suggest to some that all skill DCs automatically increase by character level and thus they felt that the game world would feel inconsistent.

If moving about a sheet of ice is a DC 10 check at level 2, it shouldn't become a DC 20 check at level 20!

Maybe the crucial passage is
But I say that's not how you have to use it. You can go the slow way and ask yourself, on a scale of 1-30, what type of character would find this an easy (or moderate, or hard) challenge - but still one he could make?
Then set that as your DC.

Running over ice might always be a DC 20 check in your campaign. Because (using the old table, not the errata) you think that a level 5st level character should find running and charging over icy terrain easy.

You can also use the DC based on other aspects. The page 42 also discusses stunts - you could base the level of your challenge on the monsters level that is to be affected by the challenge (if any) or by the amount of damage the player wants to inflict. While swinging a chandelier doesn' get harder with PCs level or the Ogres level, it might get harder to charge him with the swing or the PC want to inflict more harm with your swing.

The beauty of this rules is that you can create an internally consistent gameworld and still figure out how hard a task is compared to your PC.

You can also apply this idea to skill challenges, and in a way you are always doing this - The DCs for skills only change every 3 levels. This can be helpful if you want to run skill challenge involving NPCs - especially if it's a challenge that bypasses a combat encounter. For example, if the PCs want to trick the troll guarding the bridge into believing they already paid their toll, you could use a short skill challenge with a level based on the trolls level and a complexity that would achieve similar XP value - meaning that your PCs get the same XP if they like to role play through the encounter or like to fight through the encounter, which is usually a good thing.

In a way, this is a reverse engineering of what the 3E skill system did - DCs were usually fixed. But the fixed DC implied at which levels certain tasks become possible (when can parties hope to open Amazing locks? Of course when the Rogue's skill modifier is high enough to beat the DC with some d20 rolls.) or easy.

Of course, sometimes it would be nice to have some "fixed" DCs - a look into the PHB can help, there are a few of example DCs described in the skill selection.

It should be noted that it's suboptimal that the designers don't exactly come out to tell you that you can use the "stunt" table in this manner. I don't know whether this is because they thing it would be a rare case to work this way or it didn't occur to them. Also, the PHB example DCs seem inconsistent. As a defense it might be said that - since players don't set the DC - the players just need to see some "landmarks" what they might need. But still, a DM might want these information in the DMG, too.

Anyway, this clearly a thing that should be made more obvious. Maybe the DMG 2 will contain some hints and suggestions? Or has that ship sailed?

Mustrum_Ridcully