"clamshell mode"

I've heard quite a few people say that you should be cautious about using your Macbook closed. It might overheat. But I'm no expert and I haven't tried it myself.

Yes you can use it in clamshell mode with no problems. The vent is at the rear so you shouldn't have a problem overheating as long as the vent is clear. This is the link to apples word on the matter.

How to use your PowerBook G4, MacBook or MacBook Pro with the display closed and a Bluetooth keyboard or mouse

I use several computers at the same time in my work, and two (MacBook and one of the MacBook Pros) are connected to a Dell 20" widescreen display. They function in clamshell mode, as you call it, about 10 or more hours every day, then one of them gets tossed in a messenger bag for a trip to Starbucks or a friend's house, where I use it for a couple more hours as a notebook---this has been my routine for the past year now. I expect them to continue to function in this way for many more years to come.

You should know, though, that they do get quite hot sometimes, but I don't really worry about it. I stopped measuring temps and adjusting the fans a long time ago. 😉

i'd like to comments on this thread.
consider desktop stand which saves lots of desktop space and better for air flow.
personally, i like the style of vertical stand.
there is floater t2, but it's too expensive ($305).
there is another option, but less attractive look and feels, Power support's Docking Stand for MacBook costs $40.

In addition to other well described post,

I use my macbook for editing using FCE 3.5.x, iMovie, iDVD, and Toon Boom Studio in "clam shell"for hours everyday without overheating connected to samsung 19" ws, wireless apple keyboard and cheapo usb wireless microsoft mouse.

Try to put you macbook on a hard flat and even surface (not on a table with table cloth or fabric underneath it).

Good Luck.