Has there been any consideration to take bitcoin or litecoin or CryptoCurrency for subscription payment? Perhaps an introductory subscription of 1 month, or 3 months for bitcoin or litecoin in payment can be considered?

We haven't thought about it. It seems like a very tiny use case still, no?

It is not trivial to implement new payment methods, so unless a lot of users could pay with cryptographic currencies who couldn't pay with a credit card or PayPal, we'd prefer to focus elsewhere.

Certainly, it is an entry level consideration. Currently, the entire market cap of bitcoin is represented by a value of about $2 billion USD. The market cap of litecoin is about $30 million USD.

One method to implement payment in bitcoin, (or test the market), would be reseller associates. A Skritter subscription code for use on iTunes could be sold directly for bitcoin at a discount to associates, (wholesale bundles). Associates then resell the subscription code for use on iTunes. And an "associate" could be a website that already has a bitcoin or litecoin payment gateway, thus, the Skritter subscription code is sold to that website, (sub code bundles).

Another approach is to incorporate a bitcoin miner into your application, and there are many ways to do this. Bitcoin mining apps for iPad and smartphones are in the early development stages and botnets that tie together the processing power of many phones, or iPads are in development as well.

Users that CHOOSE to download the add-on to your app, (bitcoin miner add-on), they then pay for their subscription by providing bitcoin mining to your wallet address, (hardcoded into the miner app add-on). So while they are using Skritter, they are mining bitcoin or litecoin that is sent to the Skritter wallet.

After they pay for their subscription, they can then continue to mine for their own profit, etc ...

Early adoption is always the key in any speculative market and again, all of this depends on the continued success of bitcoin and the Crypto Currency markets, so perhaps the add-on is the best way to think about it at this time.

How about tulip bulbs? Would you accept those?

I don't have tulip bulbs, although living in The Netherlands, but I have one kidney more than I really need. How many years of Skritter does that represent ? :-)

Hehe, I would like to see crypto currencies succeed, but I think it's too early for even the approaches you suggest. The miners are an amusing idea. Bitcoin miners in iOS devices would just masticate the battery, no? What would be the hourly profit rate on those at current bitcoin prices? They don't have a lot of computing horsepower.