Depends a lot on the kitchen, but off the top of my head are: - Spills - Grease - Central point for bacteria transfers
Spills should be self-explanatory. Avoid it, that's it.
If my kitchen is an indication, your laptop might build up grease, as it passes the kitchen air inside it. However, I'm sure your kitchen is a lot better ventilated than my dungeonesque cooking central. In terms of being sticky, I would think that this is likely to happen over time, but this can probably be reduced with various methods. I have seen restaurants and the like wrap computery equipment in cellophane plastic, including a thin layer over the keyboard. Just make sure you don't cover up any vents.
I'm sure you know more about bacteria transfers and all that than I do, but an advantage to the cellophane method above is that it makes cleaning with alcohol a lot easier.
I think that the biggest concern is grease building up in the dust filter and clogging it. Consider monitoring temperatures and fan speeds. If these go astray, you might have to clean out or replace the filter. If this becomes a problem, you should perhaps have this as a part of the periodic cleaning schedule that I'm sure you have in some shape or form.
As a footnote I would like to mention that: Yes, cigarette smoke is dangerous. But I used to be a chainsmoking programmer (Now I'm neither), and I have never had a computer fail because of this. So I think that while it's far from healthy for the computer, most computers can handle it. I would think kitchen fumes aren't any worse, unless it's very humid and greasy.