Upgrades for Facebook and Yahoo sent their stock prices higher, but investors should take into account a couple of things, Josh Brown of Fusion Analytics said Monday on CNBC.

"There's really no fundamental change. There's just been this massive shift in sentiment, and sometimes that's all you need," he said on "Fast Money."

Brown cautioned against getting too bullish on tech.

"Sometimes there's just no one left to sell, and all of a sudden people decide to focus on the silver lining. So, that's great. It can go on for a long time, but I don't think anyone should say, 'Hey, there's this huge change fundamentally.' All of this is based on the expectation that things will improve," he said.

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Facebook, Yahoo and Research In Motion were among tech names that received upgrades.

"What this is about is the analyst saying, 'Look, the opportunity in mobile is way bigger than most people are counting on.' But that's a sentiment that's been out there," Brown said.

"It's just now people are choosing to decide: 'Hey, let's focus on the mobile opportunity. Let's not focus on all the negatives, and let's get positive.'"

Trader disclosure: On Nov. 26, 2012, the following stocks and commodities mentioned or intended to be mentioned on CNBC's "Fast Money" were owned by the "Fast Money" traders: Stephanie Link is long GE and AAPL; Joe Terranova is long VRTS, TJX, AAPL, SWN, VZ AND XOM; Josh Brown is long AAPL, WFC, GDX, GLD, XLU, TLT, XLF, WMT, TGT, GOOG, HD, LOW; Brad Lamensdorf: Ranger Equity Bear is short GT, COH, GMCR, TIF, BHI; Citigroup makes a market in shares of AAPL.

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