Unfortunatly, many of the reports about the Internet have been equivelent to the blind men's reports of the elephant, so here are some of the realities of the Internet. There is no way to know the number of grains of sand on a seashore. You can estimate based upon the general area of the beach, but you cannot account for the effects of the tide comming in, or the silt comming down from the river. This comment should be about something that doesn't have a unique state and thus cannot be counted. Haven't thought about what to say here yet.
Comments are welcome.
The Internet is equivelent to both phenomena. You cannot count something that changes as fast, or has no element that is unique enough to count. On the Internet a system may have multiple names, a user may have many accounts, and an account may be shared by multiple users. The Internet provides different levels of service. Any closer estimate will be invalid before the second syllable is spoken.