This has been repeated several times on the forums lately and while I wish it were true, it's not. Just to view the largest Apollo hardware left behind on the lunar surface (like the descent stages or LRVs), you'd need a telescope with 100 meters of aperture, which is about ten times larger than the biggest optical telescopes on Earth. To resolve something as small as the flags, you'd need to bump that up to 200 meters.
I think people have gotten confused about this from seeing popular articles (like this) talking about the flags still standing on the lunar surface -- but the imagery used to make that determination came from the LROC camera aboard Lunar Reconnaissance Orbiter, not Earth-based telescopes.
---------- Post added 2012-11-27 at 02:13 PM ----------
In this case, it wasn't NASA hyping anything up though. Joe Palca, the NPR journalist who was hanging out in John Grotzinger's office (Curiosity's Principal Investigator) for an interview, picked up on his excitement about the observations he and his team were working on in advance of the AGU conference. That somehow got translated into an article with the title "Big News from Mars?" and from there the speculation in the press went apeshit. This was never an official NASA announcement or statement.
What you mention has happened before though (and with disastrous results in that case), so I understand the sentiment. It's just not what happened in this instance.