shift and change over time, and reflect social constructions based on power and hierarchy.  

I no longer play the game, and when surveyed about my "race" and "ethnicity" I check all the boxes on a form, since they never give me the option to select "human".

Perhaps the best discussion about the meaning of "Latino" is at
http://en.wikipedia.org/...
It means mostly "from Latin-America" and not necessarily "speaker of a Latin-origin language."

Latino in the US, I may add, was adopted by that main "categorizer" of people, the US government, after consistent usage and pressure from political groups and social scientists.  Like all social categorizations Latino is an imperfect word, but it is a reaction to the use of 'Hispanic' to lump peoples who are nowadays, not only independent from Spain,  but resent being described as "from Spain."
As described in the wikipedia article, still some groups resent the term Latino also, because still, it lumps people into artificail categories.

More than anything, the adoption of Latino is a political gesture.

Finally, let me add that, in the vein of Thomas and Znaniecki (hoping I get the spelling right) even though racial-ethnic categorizations are "social constructions" (as pointed out in the comment below by Deoliver47) that is, they are labels, categories and concepts made up by people according to a given historical context (as well as in a power context), and are thus shifting and changeable, we cannot just ignore them because they are "real" in their consequences. This is especially true for the US, although categorizations of race are not exclusive to the US and are very common in Latin-American countries.