The 21th FarmVille Achievement (if we do not count the discontinued shutterbug) is called "They of Mystery" and is a little bit controversial though I like it extremely much.

What do you need to do?

To achieve the ribbons for this Achievement you need to open mystery boxes, and, as you know, they cost 16 FV per mystery box so achieving this one completely will cost you at least 30*16FV = 480 FV, which roughly translates into $80 you need to spend on mystery boxes in FarmVille (!)

The complete table on ribbons and amount of mystery boxes you need to buy (one of these days I'm going to make these tables dynamically):

What do I think of it?

I like it. I like it very much. I like it because it give a little giveback to players who are actually supporting Farmville by spending some dollars on it. And…  I was actually waiting for this achievement as you can see below:

So… this Achievement LOOKs like it was made especially for me :)

But I'm afraid that FarmVille just might take away this achievement because of the amount of critics on this achievement. So I will just wait for some time before opening my mystery boxes, just to be sure that nothing goes wrong here. I just wait for some confirmation in the forums that this achievement is here to stay (and I really hope it stays).

The complainers

As always whenever there is something to pay in FarmVille a huge crowd assembles to complain about the fact that they can not buy it / achieve it. And this time it is the same. The FarmVille Crews is somehow caught between running a business model based on in-game content sales versus keeping the community happy. This thread on the FarmVille Forums is probably the main discussion thread. And this is current result of the poll inside it:

So what are the complaints?

1. some people complain that they can not afford to buy FV (unemployed, kid, no money) and that basically "an essential part of the game", the achievements, now are out of their reach because this one is a "pay only" achievement. I had to laugh about this one "I'm unemployed since April... I can't afford to pay for them, the way it is I'm technically stealing internet.... I'm using a neighbors wireless since it's not pass worded.."

2. some people complain that they have spend already a lot of money on mystery boxes e.g. to get the Alpaca and only after that this achievement turns up. So they are disappointed that it did not appear earlier.

my verdict

I think that users who actually spend money on mystery boxes should now and then get a little reward for doing so and this achievement is exactly that little nice thing. Zynga / FarmVille could possibly in the future hold some more actions to hand out some free mystery boxes like they were available in the Christmas presents feeds to come somewhat nearer to people who complain that it costs money to get this achievement.
That mystery boxes were already handed out does not matter, that is the same as with all achievements. And… we have YEARS to complete these achievements. They are not ment to be achieved "within a day" but more or less indications of achievements in the game. This particular one could take the longest time for many players to achieve but it makes it more desirable to get this achievement in the end and since there are many more achievements and more coming, I think there is enough todo in the game without actually focusing 100% on this achievement.