Billguard asks for my online bank username and password, it's a deal breaker for me. Do you really trust them? https://medium.com/@hyphenated/mint-com-and-billguard-are-ly...
GnuCash has a list of OFX credentials for major banks. [2] In fact, there are tons of OFX open source libraries out there - I had luck with this one recently in Python. [3]
[1] http://en.wikipedia.org/wiki/Open_Financial_Exchange
[2] http://wiki.gnucash.org/wiki/OFX_Direct_Connect_Bank_Setting...
On its end, Yodlee is heavily regulated. Like a bank and sometimes even more: http://www.yodlee.com/yodlee-security/
That's only one part of the article though.