I am in the "one peak; one page" camp. No need to pile mountains/peaks in one page like a garage sale. Each page allows for only one elevation, one set of GPS coordinates, etc. Thus, only one peak should be on the page. Also, not all of us search by simple query. Some of us search by the dynamic maps, "what's close to THIS peak," sorted lists, etc., and these multiple types of searching are much better facilitated by the "one peak per page" rule.
If a peak isn't considered "worth" having it's own page, then don't bother putting it on SP. Maybe you don't think it's "worth" having its own page, but someone else down the road may wish to add the peak. Likewise, I see a lot of good peaks get the short shriff having to share billing with another mountain. I think of this as a form of cyber-squatting. I've seen many nice peaks on SP that are jammed into a page with 1 or 2 other peaks, and I think it's a shame. I'd be happy to build a nice, clean, readily queried page for the "red-headed step-child peak," but the mountain's already been spoken for.
A lot of folks think: Well, I did these 3 peaks together - therefore, everyone else will do them together, too. This is not always the case. In many instances, there are 3 or more sensible routes up a given peak that may or may not include "those other two" mountains. "One peak per page" allows for maximum flexibility and organization when it comes to attachments (routes, trip reports, images, etc.)
Finally, "one page per peak" is just good housekeeping. It keeps the attachments following a logical structure, it adheres to a nice database structure/heirarchy, (where one area/range has multiple mountains and where one mountain may have numerous routes and multiple trip reports etc.) Single-peak pages are less cluttered, easier to navigate, crisper.
A few other solutions to this dilema include:
1. Have the "Big Mountain" page with the "Little Named Rock Feature" as at attached child object.
2. Have only the "Big Mountain" page, but include a note on "Little Named Rock Feature" or "Other Little Mountain" in a section on the "Big Mountain" page covering other nearby mountain/peaks/crags/.
So, I say "Go for it." Go ahead and split out your mountains into seperate pages.