I agree that some achievements should remain hidden to prevent people from spamming just for the sake of getting that achievement (like having a certain number of something, blowing stuff up, etc...). But if you get an achievement and don't even know how you did it or what it means, it loses it's entire purpose. (for example: how did I get "Double Power"?)
Right now I don't see how these achievements would motivate me to play a certain way. It would be nice if there were also certain achievements where you know what to do, but that are just hard to reach. For example a perf of 900, winning a game on a certain server, having a train (TL < some length) with a high profit etc... So you know what you should try to do if you're interested in the achievement.