Capital One (NYSE: COF), the financial services company once known mainly for its “What’s in your wallet?” horde of plundering barbarians, and the flooding of mailboxes with its credit card offerings, is now in the online banking business big time.

Starting its string of bank acquisitions with Hibernia National Bank in 2005, moving on to North Fork Bank in 2006, and then to Chevy Chase Bank in 2009, it has just announced devouring yet another: this time the ING Direct unit of ING (NYSE: ING). As fellow Fool Matt Koppenheffer pointed out, many ING Direct customers found this acquisition -- to put it mildly -- loathsome.

But does that matter to Capital One? Not likely, as the deal moved it from the eighth-largest U.S. bank (in terms of deposits) to the fifth. It also makes it the country’s largest online bank, and that may be the company’s biggest motivation for the deal. Online banking, according to a 2010 American Bankers Association survey, has become customers’ preferred method for transactions. One of ING’s greatest assets, besides its (formerly) loyal customer base, is its simple-to-use website. As a customer of Capital One, I can attest that this is something the company needs help with.

Online banking security
Perhaps an underappreciated risk factor in online banking is Internet security. Many think that an update of Internet banking security standards is long overdue. The last time federal banking regulators offered any guidance on this was in 2005. As online banking grows in popularity, so does its attraction to ne’er-do-wells. Willie Sutton, the infamous bank robber from the 1930s, was once asked why he robbed banks. “Because that’s where the money is,” he replied.

That is also a modern-day truism. Hackers made off with about $2.7 million of Citigroup’s (NYSE: C) Citibank customers’ money after a May breach of the bank’s network released the credit card information for 360,000 accounts. Also not encouraging, at least for Citibank customers, is that it waited over a month to make the full extent of the breach public ... and even that announcement initially underplayed the number of accounts compromised by some 150,000. Hopefully, Capital One can do better than this.

Who’s in your wallet?
Despite these risks, online banking -- or some form of non-face-to-face banking -- is here to stay as people become more and more accustomed to the ease of online bill paying and the relief of fewer trips to branches. Capital One is smart to have increased its exposure to this form of banking. Meanwhile, ING Direct’s saddened customer base should take some Dutch comfort in their new banking situation: Things could be worse. At least ING Direct wasn’t bought out by JP Morgan Chase (NYSE: JPM), No. 9 on a Harris Interactive corporate reputation survey of least liked American companies; or, even worse, No. 6 Bank of America (NYSE: BAC); or, heaven forbid, No. 4 Citigroup. Well, you’ve got to look on the bright side.

Keep tabs on these banks -- and a hand on your wallet -- by plunking them into your Watchlist.

Fool contributor and inveterate Pollyanna, Dan Radovsky, owns no shares in the companies mentioned. The Motley Fool owns shares of JPMorgan Chase. The Fool owns shares of and has opened a short position on Bank of America. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.