The answer is that despite the similar outcome that favored positions are occupied by, and important decisions are made by, an elite group in both cases, in a meritocracy that status is earned based on talent and with elitism it is not. Confusing them can lead to two types of problems. When a system of elitism is protected as if it were a meritocracy, those who are excluded develop a strong resentment of the elites. When a meritocracy is incorrectly perceived as an elitist system, we suffer for being unable to have decisions made by the most talented people.
The truth is that we have a society that has elements of both elitism and meritocracy in it, and we have problems in confusing one for the other. A lot of ink has been spilled over this in the last 18 months, particularly around Senator Obama's remarks at a closed-door San Francisco fundraiser at which he explained his struggles in Pennsylvania as the result of "bitterness" in small-town America where people "cling to guns or religion or ..." I thought those comments were elitist, and I don't think Palin's remarks were any worse than Obama's. They share the similarity that they were talking to their base about people not in their base. That's always a risky proposition, because the latter folks will eventually hear the remarks.
The most critical manifestation of this confusion is that in a desire to tap into the anti-elite resentment in important parts of the electorate, Senator McCain selected Governor Palin as his running mate. One of her selling points to the Republican base is that she is most certainly not part of the elite. In fact, she commendably upset the established order in Republican politics in Alaska from the time she arrived on the scene. Her success in Alaska does strike a note of meritocracy, and I applaud that success. But the decision to put her on the ticket was an inspired political gamble, not the result of a meritocratic selection process for the person who would best serve the country's interests in the event that a President McCain could not continue in office.
We'll all be in a better place politically when we can get rid of the elitism, not the meritocracy.