Yodlee, an online finance web platform that directly serves banks and other financial institutions, has raised a large round of $35 million, led by banking giant Bank of America.

Although Yodlee has been something of a dark horse while popular personal finance sites like Mint have taken the spotlight, the company’s apparent success could indicate a more difficult road than anticipated for their competitors in the personal finance market, including Buxfer, Geezeo, Wesabe and many others.

The basic idea behind Yodlee is aggregation. The average American has 12 financial accounts of various types, according to CEO Anil Arora, and there are thousands of different services on offer, from banks to stock accounts. Yodlee got its start in 1999 as an aggregator of all the information from those different account types.

Today, it offers something called the Personal Financial Management Suite, which Arora called “a better, faster, easier Quicken online.” That product, in fact, is the back-end for Mint, which adds its own custom touches to help users understand where and how their money is distributed. However, it’s also used a growing majority of the country’s largest banks.

That should be worrying for independent finance sites. Most banks were very slow to add any online functionality beyond showing account balances and a list of transactions. That’s what provided an opening for personal finance sites to start up — consumers obviously want to see all the information from their various accounts in one place, arrayed in ways that are understandable. But banks are beginning to catch on, Arora says, and add the same tools to their own sites.

Given that the motivator for most people to seek out a personal finance site is a desire for things to be as easy as possible, if banks begin to aggressively use tools like Yodlee, there will be less incentive for their customers to seek out Mint and its cohorts, even if those sites continue to have an edge in visualization and functionality. In fact, Yodlee itself has only 50,000 users on its own personal finance portal, compared to 10 million who unwittingly use it through a bank.

Interestingly, Yodlee’s other big product, a recently-released bill payment solution, also sounds like a potential PayPal competitor down the road. Aside from the obvious function of paying bills from your utility, internet provider and other companies, it can transfer money between your various accounts.

Arora said you can also pay individuals, like your maid or gardener (if you’re lucky enough to have them). When I asked whether the service could be expanded, he only agreed that “other payments” could be addressed, but added, “Obviously, a lot of financial institutions are very interested in expanding transfers.” That seems to imply that other payments, for instance to a store or online auction, could be arranged in the future.

The funding, led by BoA, also brought on previous investors Warburg Pincus, Accel Partners and Institutional Venture Partners. Yodlee recapitalized with $40 million in 2002, making Warburg the primary shareholder; combined with the current funding, it has taken $75 million. It’s based in Redwood City, Calif.