Your concern is silly. People pirating applications are likely not going to be willing to pay for those applications in the first place. There is no opportunity cost associated with piracy.

If anything, in my opinion, app piracy just increases the visibility of your app and could potentially win new, legitimate users through word of mouth.

Citation needed.

Do you really think that software pirates with jailbroken iPhones that have their phones loaded up with the latest popular apps would not spring the 20 bucks or so in the app store to buy them if it were hard to pirate them? The "no opportunity cost associated with piracy" canard held water in the days where lots of commercial software was reasonably outside the reach of your average individual who wanted to play with it. But saying that little Johnny that's playing Angry Birds for free would not have bought the game for a dollar anyway is, to be frank, complete bullshit.

Not the OP, but the only people I've heard of pirating apps are those for whom $20 is the difference between eating and starving (e.g. students whose phone is paid for by family, but their food and apps are not).

A number of people pirating apps are people who don't have the App Store available in their countries, and some others are children and young teenagers who don't have their own money to buy things online (with parents who aren't interested in helping them buy games).

The worst case is when developers owe license fees for components within apps. Pirates can literally make you pay out $0.xx per pirate... Which kills profits fast.

I'm pretty sure Installous shut down from lack of use, which doesn't give much credence to your fears.