[marcusrussi]

Well, some of the bolts were already there, and I'm not sure if Tommy Caldwell and Kevin Jorgeson actually drilled any of their own bolts, but I wouldn't be surprised if they put in a few.

Bolts have always been a source of controversy in climbing – in fact, bolts were the main controversy in the first ascent of the Dawn Wall (/ Wall of Early Morning Light) back in 1970, so much that the first ascensionist's rival Royal Robbins actually climbed the route and chopped the bolts off as he went. There have been similar controversies all over the world, another notable example being on Cerro Torre in Patagonia.

Unless a climbing area is a designated "sport climbing area", bolts are generally not placed unless there is no other way to protect a stretch of climbing. Climbers try to place devices that don't damage the rock (nuts, cams, tricams, hexes, etc.) first, but sometimes none of those devices will work as they all rely on jamming against something, and blank faces do not have the cracks and holes into which jamming gear can be inserted. When this happens, bolts are placed because there isn't any other way to protect the climbers in the event of the fall.

So, I don't really have a good answer to your question except to say that the use of bolts has always and still is a huge source of controversy in the climbing community. These days, with sport "crags" being the exception, climbers try to rely on other "clean" methods of protection before turning to bolts, which is in stark contrast to past eras where bolts and pitons were the predominant way to protect pitches.

[steveax]

Important to note that Robbins changed his mind and stopped chopping bolts 2 pitches into the 2nd ascent as (according to Lauria) "the quality of the aid climbing was much higher than he had ever expected of Harding or Caldwell and, of course, it was also taking us an awful long time to chop all those goddam bolts." [1]

The seminal article on "clean climbing" was authored by Yvon Chouinard and Tom Frost and appeared in the 1972 Chouinard catalog [2]

[1] http://en.m.wikipedia.org/wiki/Royal_Robbins#Wall_of_Early_M...

[2] http://climbaz.com/chouinard72/ch_page2.html

[sliverstorm]

bolts are generally not placed unless there is no other way to protect a stretch of climbing

Which, it should be noted, describes a lot of terrain in Yosemite. The glaciated black granite provides limited opportunity for protection.

[nether]

Just watch Reel Rock 9: Valley Uprising to learn all of this.