Analyst upgrades:

• Wachovia upgraded shares of Exelon (NYSE: EXC) to Outperform from Market Perform to reflect the company's attractive nuclear fleets and strong operational track record.
  
• Jesup & Lamont upgraded Ormat Technologies Inc. (NYSE: ORA) to Buy from Hold on valuation and increasing visibility on near-term Products revenue.
  
• RBC Capital upgraded Memc Electronic (NYSE: WFR) to Outperform from Sector Perform on expectations of improved demand growth following the likely eight-year extension of the US solar tax credit program.
• AmBev (NYSE: ABV) was raised to Outperform from Neutral at Credit Suisse.
  
• AmerisourceBergen (NYSE: ABC) was upgraded at Merrill Lynch to Buy from Neutral.
  
• Piper upgraded Anadys Pharma (NASDAQ: ANDS) to Neutral from Sell.

Analyst downgrades:

MOST NOTEWORTHY: Telefonica, Affymax and Hatteras Financial were today's noteworthy initiations:

• Deutsche Bank initiated Telefonica (NYSE: TEF) with a Buy rating and believes concerns of an economic slowdown in Spain are overdone and that company is on track to make 2008 guidance.
  
• Baird assumed coverage of Affymax (NADAQ: AFFY) with an Outperform rating and $25 target. The firm believes the market has discounted the regulatory and commercial prospects of lead compound Hematide, which they believe is a $800M revenue opportunity, and recommends buying shares aggressively in the mid-$20s.
  
• Shares of Hatteras Financial (NYSE: HTS) were started with an Outperform rating and $35 target at Friedman Billings. The firm believes management has the opportunity to stabilize its agency portfolio and generate a return on invested capital of about 20%.

OTHER INITIATIONS:

• Caris assumed OmniVision (NASDAQ: OVTI) with a Buy rating and $15 target.
  
• Pioneer Natural (NYSE: PXD) was initiated at UBS with a Buy rating and $110 target.
  
• UBS also initiated CME Group (NYSE: CME) with a Neutral rating and $430 target.
  
• Allied Capital (NYSE: ALD) was assumed with a Buy rating and $14.40 target at Merrill Lynch.

MOST NOTEWORTHY: Marvel Entertainment Inc (MVL) and Affymetrix Inc (AFFY) were today's most notable initiations:

• Sanders Morris started Marvel Entertainment Inc (NYSE: MVL) with a Buy rating and $34 target on the belief that 2007 guidance is conservative.

• Thomas Weisel initiated Affymetrix Inc (NASDAQ: AFFY) with an Overweight rating and is positive on Hematide, their lead drug, to treat anemia.

OTHER INITIATIONS:

• Morgan Stanley initiated Emmis Communications Corp (NASDAQ: EMMS) with an Equal-Weight rating and $10 target.

• Nollenberger started LSI Logic Corp (NYSE: LSI) with a Neutral rating and $10 target; they believe it will take several quarters for the LSI-Agere business plan to pan out.

• Morgan Keegan believes shares of Buffalo Wild Wings Inc (NASDAQ: BWLD) are fairly valued, starting the company with a Market Perform rating.

Analyst summaries provided by TheFlyOnTheWall.com (subscription required).