If you have significantly less culture the chance of 'flipping' (god I hate that word, why isn't it called revolting???) is much greater. Try a deity game, with an early war, take over your opponents captial a number of turns after he's built a wonder. Just try holding the city, sure, rushing temples helps but if you don't even have time for the city to get out of resistance before it flips back then you're not going to get the temple, and basically there is nothing you can do to avoid it. So I make sure to raze all my opponent's wonder cities and his captial.