"Micron is undershipping demand in DRAM, as technology migrations limit supply output," writes Nomura's Romit Shah, downgrading Micron to Neutral and cutting his target by $10 to $30. He also thinks the memory giant "seems behind on technology transitions," and that FQ3 (May quarter) estimates are too high.

Shah believes Micron has lost a couple hundred bps of DRAM share to Samsung, and expects bigger DRAM/NAND investments in 2016 in order to sustain share. His 2015 and 2016 EPS estimates have respectively been cut by $0.30 and $0.86 to $3.35 and $4.00.

Shares are below $30 for the first time since Feb. 10. They sold off last week following a downbeat Cleveland Research note and a report that Samsung would be supplying mobile DRAM for the iPhone 6S, but pared their losses after analysts defended the company and Micron offered positive remarks at a Susquehanna conference.

Nomura upgraded Micron to Buy in Dec. 2013, when shares were at $22.50.

Update: More details on Nomura's downgrade here, as well as a defense of Micron by Needham.