SAN FRANCISCO, Sept. 28 — Since the iPhone hit the market in June, tech-savvy owners of the phone have been busy messing with its insides, figuring out how to add unauthorized software and even “unlock” it for use on networks other than AT&T’s.

But the Web was filled Friday with complaints from people who had installed the latest iPhone software update, only to see all the fun little programs they had been adding to their iPhones disappear — or, still worse, see their phones freeze up entirely.

Should they have known better?

Since Monday, Apple officials have been warning iPhone owners that using unlocking software could cause the phone to become “permanently inoperable when a future Apple-supplied iPhone software update is installed.” But in many cases those warnings went unheeded.

People who had unlocked their phones to use them with another carrier ran the greatest risk of, in techie terms, having them “bricked” — rendered about as useful as a brick. Most of those who committed the lesser transgression of installing programs not authorized by Apple simply had those programs wiped out.