I’m using over 99% of my laptop’s 114GB SSD hard drive, so every GB counts. Recently I tracked down an application that was taking up more and more disk space: bitcoin-qt, the reference bitcoin client software. Bitcoin-qt keeps a local copy of the entire blockchain history, which makes it more secure than clients which rely on the network to be free from attackers, or rely on a remote server to verify the blockchain. However, the blockchain is only getting bigger.
View the blockchain size (currently about 13GB and growing)
And on my local machine
~ $ du -h .bitcoin/
If you have limited hard drive space, you might have to trade off bitcoin security for space. To make an informed decision, read up on what options you have. It is possible to use a thin client on a laptop that does not verify the blockchain. These thin clients work well on smartphones.
I am sadly aware that scary blog posts about bitcoin only make the bitcoin world less inviting to newcomers. If you want to get started with bitcoin, I recommend making a coinbase.com account, using two-factor auth and a great password, and keeping your bitcoin in their online wallet. Then, you can transfer a small amount, like $1 worth, to a local wallet to experiment with. Remember to back up your local wallets.
Personally, I am installing bitcoin-qt on an older machine that has a magnetic hard drive and plenty of empty space. Then I will transfer my bitcoins off of my SSD machine and delete this local copy of the blockchain.