They're watching us - and what we do when we shop online.

How we buy stuff reveals to companies and advertisers important details about us: how long we linger on a website, hunt around for prices, then decide (or not) to purchase; what ads we click on social media; and how many dollars we spend.

The data equal money. And Conshohocken-based Monetate is the company monetizing our personal information for retailers.

Lucinda Duncalfe, Monetate's CEO, explains: If you're reading this story online, for instance, the advertisements you see may differ from the ads everyone else sees.

"If you and I both visit, mine looks different, and yours look different. Monetate enables that," Duncalfe said.

Founded in 2008, Monetate personalizes marketing to you, and you, and you. That email link you open every morning from your favorite retailer looks different from the one in your mother's inbox, and the one in your neighbor's.

"That email looks different if I'm walking down Chestnut Street past the store in the middle of the day, vs. at home at night," she adds.

Monetate is part of the latest generation of Philadelphia-area tech concerns that could go public one day. It has already raised $48 million in funding in three rounds, initially with First Round Capital and OpenView Venture Partners in Boston.

"We've got deep Philly roots. The founders and I are all Philly people. The city has some big advantages and disadvantages," Duncalfe says. "People are very reasonable and not mercenary the way Silicon Valley is mercenary, and yet super-talented. It's a nice balance."

A native New Yorker and the daughter of artists, Duncalfe played basketball at Penn, graduating in 1991. She returned to Philly after stints in Silicon Valley and New York, got engaged, then applied to Penn's Wharton School.

At Wharton, she found the leadership skills she got through athletics were valuable in business.

"Here was this thing that had an intellectual underpinning," she said, "and I didn't have to be poor, since I grew up without any money."

Monetate has grown to more than 200 employees, now also has offices in Palo Alto, Calif., and London, and is branching into travel, publishing, financial services, and health care.

Would Monetate fetch $1 billion in an initial public offering, vaulting it into "unicorn" territory?

Duncalfe demurs.

"I'm pretty sure the air is letting out of the balloon a bit here. The devaluations of some unicorns is happening by mutual funds. It's actually a complicated map right now."

But she says she's not worried about hitting a certain valuation number. The second-generation tech boom is fuel enough.

"For Monetate, it's positive. We are a relatively conservative company," Duncalfe says.

Competitors, which include Adobe, Optimizely, and Qubit, "spend at a burn rate of 100 percent plus for growth. That's not our philosophy. That requires constant capital, a huge burn rate to feed that beast. We take a much more conservative approach with a slightly slower growth rate."

Duncalfe won't disclose numbers, but she says that Monetate is "cash-flow positive" and that it won't raise venture money again.

Would she prefer that Monetate be acquired or go public?

"We don't have an answer. Philosophically, you grow companies to be independently successful; if you sell along the way, you sell along the way. Our internal goals are all driven off of metrics that are used to go public. If something happens, it happens."

In terms of market share, Duncalfe doesn't disclose numbers. But she does say $100 million in revenue is "IPO-able." That's the industry standard for SaaS (software-as-a-service) companies.

"Our absolutely number-one goal is market leadership. That's the endgame," she says. "That means people in our industry think of us as Number One not just in retail, but in travel, financial services, and health care."

Monetate's current customers include Vera Bradley, AutoZone, Ray-Ban, DirecTV, Macy's, QVC, Office Depot, Patagonia, Sur la Table, and the North Face.

Among the nuggets of data Monetate has mined: Shoppers on mobile devices often place smaller orders. And the smaller the screen, the lower-priced the purchase.

During Cyber Week 2015, Monetate claims to have influenced more than a third of the $11 billion in total U.S. e-commerce sales, or one of every three dollars spent online.

U.S. online sales on Thanksgiving Day gained 25 percent, to $1.1 billion in spending, the first day of the current holiday season to reach that level. Black Friday followed with an even stronger spending day, with $1.66 billion in desktop online sales, up 14 percent from last year, according to Web analytics firm comScore.

Cyber Monday 2015 beat out Cyber Monday 2014 by 16 percent, with more than $3 billion in online sales, the highest ever.