PMland serves other purposes here in AD, such as to confide with another member, to say, 'hello!', to simply get to know another person better, as you can see, there are many reasons for using PMs, like for myself, I can't ignore the influx of PMs I do get daily, there are many times some of these members are asking for help, advice, etc., or simply have a complaint that needs attention--with my PMland hovering near 200 almost daily, it's always hard to choose which ones I do want to 'delete' or 'save'....of course, I could always save them to a file on my computer....
Bottom line, I can't nor will ignore anyone who PM's me, as for those who don't reply back, often-times, they don't have the habit of checking their PM's as much like some members might. If after several tries and to no avail, then simply move on...there's plenty of others here who would happily respond to a PM!