[nkristoffersen]

Seems like bad practice. Do a lot of people do that? Why would I share the same GA code between all of my sites? It would taint my analytics data and make the analytics worthless, no?

[aarreedd]

Google analytics tags look like this: UA-1234567-1

For each site the last digit increments. We only use the part that stays the same.

However it is fairly easy to get actually unique GA codes under the same account. But many people do not do that.

With AdSense you cannot get a different publisher ID unless you set up a whole new account.

[netzone]

And the places where this happens a lot (ads for example) is completely useless for this.