Facebook shares hit a new low last night as they fell to $17.73.

It was the first time Facebook shares have fallen below $18. They fall puts the stock almost $21 off of the $38 IPO price.

The latest drop in Facebook comes as analysts at Morgan Stanley and JPMorgan Chase cut their targets and long-term outlooks for the social networking site’s shares. 

The two investment banks were the biggest underwriters of Facebook’s IPO in May and according to the FT one Morgan Stanley analyst said in a note to clients that “the shift of Facebook users to mobile continued to hurt the company’s revenues despite improvements to its ad formats on mobile in recent months”.

As the stock fell yesterday Facebook issued a statement saying that chief executive Mark Zuckerberg had told staff that “he has no intention to conduct any sale transactions in our securities for at least 12 months”.

Earlier this month Facebook shares  fell as the post-IPO share lockout ended. The subsequent fall in Facebook stock was more than double the decline indicated in pre-market action.

The continued downward spiral of Facebook stock mirrors activity at Groupon and Zynga.

Earlier this month Groupon shares hit a life-time low of $6.05. That was two weeks ago. Its shares have fallen sharply and were last night trading at just $4.24.

Likewise, Zynga, which is closely linked to Facebook has suffered. Shares in the FarmVille and PetVille game maker fell to $2.95 after it lost its COO.  Last night they fell as low as $2.67 before rallying slightly to $2.83.

As for Facebook the FT reports that employee shares will hit the public markets on October 29. This is two weeks sooner than expected.