You're incorrectly assuming that kowledge can be gained from TV or internet only. Witness this exchange from Small Favor:
"Ivy is the Archive," I said quietly. "A long time ago-we don't know
when-somebody-we don't know who-created the Archive. A kind of
"What?" Sanya asked.
"A kind of entity composed of pure information. Think of it as
software for the brain," Luccio said. "Like a very advanced database
"Ah," Sanya said, nodding.
I arched an eyebrow at Luccio in surprise.
She shrugged, smiling a little. "I like computers. I read all about them. It's...my hobby, really. I understand the theory behind them."
So the implication is that since wizard can't work with electronics they have to go to second-best source of information after The Internet: periodicals and books. And it's not unreasonable to assume that wizards read A LOT - can't have TV or radio, can't have computers... and they sometimes have A LOT of free time on their hands. And not all of them have a company... for cold autumn/winter evenings... Witness below exchange from Proven Guilty
His phone buzzed again. He stepped away and spoke quietly, his back to
us. After a moment he snapped his fingers and said, "Glau, get on the
computer. The auction is closing in five minutes and there's always a
last-second rush. We'll need to verify an account." He turned back to
the phone. "No, unacceptable. A numbered account only. I don't trust
those people at PayPal."
"Hey!" I protested. "Are you selling me on eBay?"
Crane winked at me. "Ironic, eh? Though I confess a bit of surprise.
How do you know what it is?"
"I read," I told him.
That Harry actually know what is he talking about, see below quote (and last words specifically), again from Proven Guilty and same chapter:
It came down to this: If I didn't hear her out and didn't get out of
this mess, Rawlins's blood would be on my hands. And whoever was
behind the slaughter around the convention might well keep right on
escalating. More people could die.
Oh. And I'd wind up enjoying some kind of Torquemada-esque vacation
with whichever fiend had the most money and the least lag.
Internet Revolution was not instant. I remember very well that for quite a while quite a few periodicals made very good money off of every kind of guide to electronics, software and computers in general. It's only recently (several years, I mean) that most content is now if not online exclusive, then at least available there, too...
Also, a quick internet search revealed that in US alone there were at least three magazines about parkour, going as far back as 2005 and still in business in 2008. Parkour itself is even older - i just read the article about it written in 2002...