U2 posté a formal news announcement regarding unfounded rumors of tours and to beware of ticket scams.
Check it out on: link
As quoted from U2 Official fan Club Site news on January 7, 2009:
"Just a note to correct some online information suggesting that tickets are available for U2 shows this summer. No tickets are available and no shows have been announced.
There are no tour dates for the band at the moment so please don't get stung par buying tickets for shows that don't exist.
toi can be sure any future live announcements will be made on U2.Com as soon as details are confirmed."