Shares of ValueClick (VCLK) slipped Wednesday after one analyst suggested that the chance of a buyout had faded.

ValueClick's stock has climbed almost 50% since the start of the year after a wave of takeovers hit the online ad space. The rich 85% premium paid for rival

aQuantive

( AQNT) by

Microsoft

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last week further emboldened investors to bid up ValueClick.

But the chances of a buyout are dampened since major Internet players such as

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Google

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,

Yahoo!

(YHOO)

and Microsoft -- as well as two ad agencies -- have already made acquisitions in the space, Credit Suisse analyst Heath Terry wrote in a research note on Wednesday.

"ValueClick has gone beyond our estimated standalone valuation and we are not willing to rest our investment case for further upside on a potential takeout," Terry wrote, downgrading the stock to neutral from outperform. Credit Suisse had placed a $32 price target on the stock.

Also beginning to weigh on the company was its disclosure in a regulatory filing on Friday that the Federal Trade Commission is investigating some of its business practices.

Shares of ValueClick were recently off 91 cents, or 2.6%, to $34.09.