I started having problems a couple of months ago, using the Mozilla reader through my ISP. After first denying the problem, the ISP finally admitted the link they have through the phone company was unreliable to the news servers. I thus had to use dejanews (now google). Every thing was fine for awhile, but now I to, like Tom, seem to find the message counts way down, and occasionally one of my posts does not make it. I suspect there is getting to be a system wide problem.
One problem may be that by far most net users do not use (nor are even aware of) newsgroups. Thus, any problems seem to be of very low priority to both the ISPs and the network companies. I suspect that now adays only about 2% of inet users even know that newsgroups exist.