I've spent the last two years doing mostly PHP dev (small company doing web dev for other small companies in a small town), and while I've never personally used it PEAR is still included in cPanel Apache PHP builds, so I'd hazard a guess that there are a number of servers who are still using it (at least marginally) even if they don't realize.

That said, this would really only apply to someone who rebuilt their Apache instance in the last six months, or manually re-installed PEAR. It has the potential to effect big cPanel based hosting companies like GoDaddy, but only if they were deploying new server instances and not using an image to do it (for some reason).