In a previous encounter I filled a room with a bunch of chairs and tables with the intent of players run around or over them to escape a difficult creature. I wasn't sure what the penalties were so I just had them roll acrobatics or athletics whenever they ran over a piece of furniture, and I was curious as to what the actual penalties were.
D&D 4th Edition doesn't appear to define it, and that isn't surprising. Unlike previous editions, 4e doesn't care so much about simulating the world or engaging in that level of detail. It offers much more high-level abstract rules alongside suggestions about how or when to apply them, and the designers weren't interested in going into such a specific level of detail as providing specific rules for moving over furniture.
4e will offer you some terrain types to base your own off, or various suggestions in the rules, and it's ultimately up to you as the DM to decide how you want to run this. As long as you and your players found the way you approached that terrain to be fun, what you did was perfectly fine.
One suggestion is offered: the description for Difficult Terrain (PHB p284, or RC p310) specifically mentions moving over "low furniture", and difficult terrain means "each square of difficult terrain costs 1 extra square of movement to enter."
However: this is a guideline or example of when to use difficult terrain, not a rule as to when you must.
You're free to make a judgement call about when to use this. What furniture counts as "low furniture" is left up to you (which should reinforce that this is only a guideline): depending on your interpretation, it could be any furniture shorter than you, including chairs and tables but discounting tall cabinets and thrones - or it could be anything below waist height.
You're also free to govern movement over low furniture some other way (or via some other sort of terrain rules), or ignore it completely and have it provide no mechanical influence (your player characters can just shove it out of the way whilst running, or whatever).
The answer is DM's discretion.
However, Keep on the Shadowfell (H1) describes what to use for beds and tables, at least for that adventure: