United States District Court Judge Ronald M. Whyte (Northern District of California) granted in part a motion to certify a class of citizens of California who on or after March 23, 2003, purchased via Dell's web site Dell-branded products advertised with a represented former sales price.  Brazil v. Dell, Inc., 2010 WL 5387831 (N.D. Cal. Dec. 21, 2010) [not to be confused with the Court's Order on a motion for judgment on the pleadings filed the same day].  The Court offered this interesting discussion concerning reliance:

In California, “a presumption, or at least an inference, of reliance arises wherever there is a showing that a misrepresentation was material,” In re Tobacco II Cases, 466 Cal.4th 298, 397 (2009). Materiality is an objective standard, see U.S. v. Watkins, 278 F.3d 961, 967-68 (9th Cir.2002), and is susceptible to common proof in this case. There is no dispute that the alleged misrepresentations were communicated to all class members, because the representations were made at the point of sale as part of a standardized online purchasing process.

Plaintiffs point to common evidence sufficient to show that the representations were material to plaintiffs. Although Dell points to some testimony from plaintiffs that it says “fails to establish legally sufficient reliance for even their individual claims,” the court finds that testimony read in context sufficiently indicated that the plaintiffs relied. There is evidence that Dell considered the representations material, and that external reference prices and semantic clues impact customers' perceptions of value and purchase decisions. Dell's marketing expert contends that while some purchasers may attach importance to a discount off Dell's list price, others will base their decision on wholly unrelated factors. But under California law, plaintiffs need not establish that each and every class member based his or her decision on the represented discounts. Plaintiffs' common evidence that the representations were material satisfies California's reliance presumption and Rule 23(b) (3)'s predominance requirement.

Slip op., at 5.

A similar practice by Dell almost caught me about a year ago.  I ordered a computer on the basis of a claim that I was receiving a special, limited-time discount.  I then discovered through another source that the prevailing price at the time was lower.  I cancelled the order before it shipped and re-ordered at a significantly lower price.  I'm pretty happy with Dell computers from a hardware standpoint, but their sales tactics have some room for improvement.