STORY: Brown says, "it may not you know, happen tomorrow, but at some point some of these stocks, which are already a huge part at least of the US market... have to come down."
She adds they may be giving investors a false sense of their performance in this market as the strong performance of large technology stocks masks the performance of the rest of the market.
"What that also means is the average stock is not going up. And so to me that translates into that, unless you're, you know, kind of overweight in some of these technology names, you're probably underperforming the market. And depending on how much you're underweight your, you know your portfolio may be flat even though the market's up," Brown says.