Problem is when you procrastinate because manually importing transactions and correcting them is just annoying enough to make it a hassle. Then the transaction batch gets too large and you can't remember details anymore so you give up and don't track your budget at all.
That's been my experience in the past at least.
I don't know, I'm really interested in all these internet services that are 100% safe from hackers. Sounds like very useful information that should be shared around.