The list of companies going public keeps growing. Sixteen companies are expected to begin trading publicly just this week, making it the busiest week for IPOs since 2007. But are there signs investors are souring on IPOs?

Some of this year's highest profile IPOs -- namely King Digital (KING), parent company of the extremely popular game Candy Crush -- flopped with investors. King Digital stock is down 19% from its offering price. An ETF that tracks the performance of new IPOs has dropped about 2% this year, and some recent IPOs have priced at the low end of their target range.

Ally Financial (ALLY), the former financing arm of General Motors (GM), debuted Thursday on the NYSE at $24.25 a share -- 3% lower than its IPO price. Ally is the largest IPO so far in 2014 after the Treasury Department sold 95 million shares, raising $2.38 billion in the deal. Hotel chain La Quinta (LQ) raised a lower than expected $650 million in its IPO this week, reports Bloomberg's Leslie Picker.

In an interview with The Daily Ticker, Picker says IPOs are missing expectations because they're "technically momentum plays," and momentum stocks in general have been beaten down by investors.

Related: Growth vs. Value: Has the worm turned?

One bright spot in the IPO market has been GrubHub (GRUB), the online and mobile food offering service.

"Bankers are pointing to GrubHub as proof that the IPO market is still strong," says Picker. "Investors couldn't get enough of it. But it could [still] be challenging for other companies in the [IPO] pipeline."

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