[mihaifm]

The Wonder mechanic has always been like that in Civ games, and I would prefer it to stay the same. You can rely on scouting to make sure no one else builds it. If you can't scout, you need to evaluate the risk and decide if it's worth it.

[OskarS]

It hasn't always worked like that. In earlier games, if another civ built your wonder, you could switch to building something else and retain like 75% of production (don't remember the exact numbers). That meant you didn't lose a massive amount of production in one of your most important cities for no good reason.

(I should say: it's been a while since I played the earlier Civ's, but I'm fairly certain this is how it worked. It's certainly works this way in Alpha Centauri, the best game in the series!)

[moreira]

In Civ 2 at least, if you switched to another wonder you'd keep -all- your production so you could just shrug and switch to another wonder without losing anything. It's only if you switched to a normal building or a unit that you'd lose 50% of the production.