There are many ways to manage your finances online. There are websites that you can use to track your finances via the internet. You enter your details and some of these sites download your financial transactions and create charts and reports for you.
The principle is right, you need a way to keep track of your expenses. But I prefer to do that in my local machine instead of on a hosted environment where my detailed financial information is maintained by someone that I don't even know.
At the end of the day, these websites are maintained by people, all you need is one dishonest employee with access to the database and he/she can steal your identity and, potentially, your money.
These websites have very strict rules and they assure you that they are always doing all that they can to keep your data safe, nevertheless all you need is one person and the damage is done.
I support the internet and all the wonderful things that we can do with it, nevertheless, I don't think that it is safe enough to be giving out detailed personal and financial information to perfect strangers on the internet. After all, would you give out your bank account numbers, and how to get to them, to a stranger on the streets? So why would you do it to a stranger on the internet?