See, I really have problems with these sweeping, and forgive me, rather banal comments.
Mainstream? Corporate? U2 are just as corporate now as they were back in the early 80's, when the had T-shirts and video of their concerts and singles and remixes (yes, remixes). I mean, they released "Wide Awake...", a 4-track EP between albums. We praise "Wide Awake..." now, but if U2 released a little 4-track EP right this very moment, we'd all claim how "corporate" they were and how money-hungry they are. We zoom on in the iPod commercial, completely and conveniently forgetting that Larry did a Harley commercial back in the 80's! We poke fun at their U.S. TV appearances now, forgetting how often they appeared on Irish and UK TV back in the 80's. I see zero difference between now and then. U2 were always about being the biggest band and that hasn't changed. And part of being big is working within the corporate system. KISS, yes, KISS, knew this back in the 70's. They had action figures of themselves, along with lunch-boxes and crappy TV shows. Yet, now, they are still respected as "rock gods". Working within the system gains necessary exposure to ultimately get your message out. U2 learned this early on - and Bono is now fully exploiting this fact for DATA.
As for quality of music, just as I wrote above, when ATYCLB and HTDAAB were released, they sounded like nothing on the radio at the time. So what exactly makes them "safe" releases? The one time U2 were "safe", oddly and perhaps ironically enough, was with "Pop". U2 tried to emulate sounds they heard by other artists (like Prodigy and the Chemical Bros.). Then they mixed that in with Beatle-esque tracks. We all know the result. In other words, when U2 tries to blend in, they don't succeed nearly as well as when they go their own paths.
So please don't dismiss them as being "corporate" and afraid of change, because the only evidence I've seen of this came in 1997, from an album that people here claim is so "different".