In recent months, I've noticed an interesting misconception.
Some observers - notably from North America - seem to be under the impression that netbooks are, by default, mobile-connected. And, in particular, that they are major contributors to 3G data traffic.
As far as I know, this is not really true. Yes, in the US (and, I think, Japan), a fairly decent proportion of netbooks are sold through mobile carrier channels, with embedded or bundled 3G modems, usually on monthly plans.
Elsewhere, although that model exists, it is far from the most important. The majority of netbooks are sold through ordinary PC retail, corporate or online channels. And these generally do not have in-built wireless modules. Yes, some get used with USB 3G dongles (such as the one I'm writing this post on, from my local cafe), but many are just used with WiFi or even ethernet.
In 2010, there will probably be around 40m netbooks shipped. I'd be surprised if more than 10% are sold with built-in 3G, with maybe another 10-15% used with separate dongles. Ordinary retail netbooks rarely ship with 3G modules, as the cost is a very large % of the manufacturer gross margin - so the OEM won't wear the cost unless they're certain of either getting a higher retail price (unlikely as dongles are cheap), or some form of bounty from operators when/if customers sign up (rare).
The majority of PC-based mobile broadband traffic is generated by ordinary, larger *notebooks*, not netbooks, as both the installed base and new shipments are far higher than those for netbooks.