I can't see where it's necessary on a bike tour, unless you plan on a long off-road tour and want to just throw the thing around, leave it outside, or maybe tie a rope to it and drag it behind the bike.

I've toured with a $250 Acer Aspire One and have had no difficulties whatsoever. Like Tourist in MSN, I have one of those neoprene sleeves to keep it in, and I always pack it vertically in a pannier so there's nothing putting weight on it. I pack it in the middle of the (waterproof) pannier and pack soft things (like clothes or a towel) around it. Never had a problem. A couple of years ago my touring partner carried an identical one on our 1800-mile tour of Central America, including about 100 miles of rough dirt and gravel road riding. She packed it the same way, never had a single problem. And both of these have the traditional hard drives, not the solid-state ones.

Also, some of those rugged ones weigh a ton. One was over 8 pounds! One (forget which one) was quite light at 2.3 pounds, but definitely not cheap. Save the money and just get an inexpensive netbook.