Hi. I'm experiencing the same problem (intermittent Safari crashes). I tried the following fixes:
1) Restoring iPhone from a backup
2) Erasing everything from my iPhone
3) Disabling Safari iCloud
None of which solved my problem.
I can replicate the crash by going to CNN Web site and clicking on "Show Comments" under an article. Safari either crashes when loading comments from a Disqus system or when trying to create a new comment. Interestingly, this issue is not specific to Safari - I'm having the same problem when using Chrome. This tells me that this is really OS-specific, and it all worked fine uner iOS 6. The new OS version is worse than Windows (and not only because of this issue).