Some reviewers of the Nexus 7, while giving it praise, are hitting the 7" tablet on its lack of 3/4G capability.
The Nexus 7 is a wifi only 7" tablet using the Android operating system. This author can confirm it is a very popular item, as three people so far in my office have purchased the device.
Reviewers, though, are upset about the lack of 3/4G capability in the device. The complaints have gotten so loud, Google put out a commercial on the Internet. As the reviewer on TechCrunch put it, not having the added capabilities means it won't keep the kids occupied on long trips, the reason he has for purchasing such a device.
Here is the Google commercial video: