The last stock Mark Cuban bought was J.C. Penney.
The billionaire investor and entrepreneur told CNBC's "Street Signs" on Friday that he bought 1 million shares of the retailer a "couple days ago."
He also said the rise of activist investors like Carl Icahn has become a reflection of what the stock market has become.
"It used to be the thought was when you owned a share of stock you owned a part of the company," Cuban said. "We're no longer owners."
(Read more: Mark Cuban: 'I rarely invest in stocks')
Instead, people just trade in and out. "It's become a platform more for hacking than for company ownership," he added.
Cuban also is the lead investor in an education start-up called Ranku, which he believes will help shake up the education business given the soaring cost of tuition and the mountains of student debt.
"There's a bubble right now in tuition costs for higher education and that has to change," Cuban said.
"Parent can't afford to send their kid to traditional schools," he added, and Ranku will show the alternatives and benefits of getting an online degree. He likened the service to Kayak, the online travel site that searches hundreds of travel sites at once.
Ranku founder Kim Taylor said: "People are just going to shop for degrees based on job outcomes. We want to close the skills gap and push people to better decisions."
(Read more: A quarter of recent college graduates lack jobs)
But the site does not include the for-profit education companies like Apollo. "People just aren't getting their money's worth," Cuban said of the for-profit education companies.
Apollo spends so much money on promotion it creates the illusion you're going to get value, Cuban said.
He also said that to get tuition costs under control, there should be a limit on student loans that are guaranteed by the federal government.
"All of a sudden you'd see the price of tuition just crater," Cuban told CNBC.
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