We continue our Wall Street technology series with a look at high-frequency trading, where powerful computers can make hundreds of thousands of trades in milliseconds, making big money off tiny stock price differences. And password management company SplashData is out with its annual survey of the most common passwords. For the first time, a new terrible password is on top. The most common password is “123456,” beating out the reigning champion, which is just “password.” Either one is a fine invitation to get hacked.

Target and Nieman Marcus customers are among the tens of millions whose credit cards have been compromised in recent hacks. The news is sparking a lot of questions about American credit card security. That brings us to the next part of our series on Wall Street technology. Today, we’re looking at why American banks and retailers are still using the same old magnetic strip cards, instead of more secure chip and pin cards commonly used abroad.

It’s Friday, which means it’s time for our weekly numbers game, Silicon Tally. This week we play with Marketplace technology reporter Queena Kim. And Facebook is taking a page out of Twitter’s book. Facebook will now offer users a list of trending topics, so they can track what folks are posting about. It’ll roll out to American accounts in the coming weeks, tailored to user interest and location.

A Ford executive recently whipped up controversy when he said the carmaker knows when drivers of its cars break traffic laws. Ford’s CEO later said that Ford doesn’t — and won’t — track cars. He also called for better privacy laws as cars add new location-based technology. And a new study from Georgia Tech looks at how words you use can determine whether your Kickstarter campaign reaches its goal.

One piece of news that maybe won’t blow your mind is that our mobile use around the world is way, way up. In 2013, it grew a 115 percent over the previous year. That’s according to mobile analytics firm Flurry. Why? Well here’s the interesting part: A lot of things drove growth. Music and other media, games, news all played a role. But the big kahuna of mobile usage last year? Messaging. Simply: The new ways in which we communicate.

If you’re selling a successful startup these days your price tag should have several billion dollars on it. That seems to be the going rate, and smart thermostat maker Nest just got snapped up by Google for $3.2 billion. Nest’s CEO Tony Fadell once worked for Steve Jobs designing iPods, now his direct boss will be Google’s Larry Page. And one more bit of acquisition news. Facebook has bought Branch and Potluck — platforms for long, invite-only conversations online. The people behind those companies will now help run the new Facebook Conversations Group. Talk ain’t cheap in the tech world I guess. The deal? Reportedly worth $15 million.

There’s already been a lot of talk about the growth in wearable technology in 2014. But a lot of that technology seems designed for the male sex. Still, there are glimmers of diversity on the way. The San Francisco company Fitbit, which has become one of the more popular makers of wearable fitness trackers, just announced a new partnership with women’s fashion designer Tory Burch.

Marketplace Tech has been talking about the International Consumer Electronics Show all week. And on the last day of CES, we’re starting to get a sense of this year’s offerings. One takeaway is that there is no one takeaway. We saw updates of smart devices and the ways they might talk to one another. And wearable technology is seeing a bunch of growth. But even if the future of 2014 is bright, it’s not really in focus yet. Plus, the production designer of “Her” discusses designing the ways we interact with technology in the future.

Earlier this week, Intel announced at the International Consumer Electronics Show in Las Vegas that it’s getting serious about mineral sourcing. Where companies get the ingredients for our chips and our devices is kind of a dirty open secret. And until the creation of new materials, it will stay that way. But the world’s largest chip maker is promising all of the microprocessors it ships this year will be free of conflict minerals.