It downloaded 500MB on my SSD and I stopped it, I've read that it has to download about 15GB. Thats too much for me. Do the other projects download such big blockchains also ? I mean 15GB for each project ?
In theory though, through the magic of Merkle trees, a superlight client could get away with needing only a few KB of storage, accounting for the paths through the Merkle tree that witness its spendable outputs. A discussion about such a setup for Bitcoin can be found for instance at
https://bitcointalk.org/index.php?topic=88208.msg1896213#msg...
I don't know of any crypto-currencies that have implemented these UTXO commitments that would allow for such wallets though...
1. Geth/Mist now supports a "light client" mode that requires much less storage and maintains most of the strong crypto guarantees.
2. Most of the size problem is due to the complexity in efficiently optimizing the serialized data, this will improve in the near future.
3. Ethereum is on the forefront of research into scalable blockchain technology, which has the potential to resolve this problem.