Larry David 37% "Native American" and Jessica Alba only 13%?
Methinks this is due to inflated Native American DNA estimates, a problem which has plagued this particular test. As far as I know Larry David is Jewish in ancestry, so I would expect a much higher "European" component.
Alba is apparently half white Canadian and half Mexican American. A figure of about 1/3 Amerindian ancestry has been estimated for a sample of US Hispanics from New Mexico which would seem consistent with Alba's estimated ancestry estimate.
All in all, I would say that these results tend to confirm that while the AncestryByDNA test tends to provide reasonable admixture estimates (within its statistical limitations) for actual admixed persons, it is less valuable for non-admixed individuals who are not a good match for the four chosen ancestral sample groups.