Yes.  Unfortunately portals are one of the most highly marketed but under delivered features of DotNetNuke.  Anyone on our support team can probobally tell you every single customer of ours who is running lots of portals because those are the sites that are _always_ having problems (the way that portals work encourage people to do not-smart stuff).  For example, Just yesterday one of our support guys called me over to look at a DotNetNuke site that had over 190 modules installed on it (I didn't know that many even existed!!!).
 

All in all, I think portals have their place, but it certainly isn't in production for a business critical system.  They're great for having a test bed (on a different installation from your production site), for playing around with modules, and for a few small & non-critical websites.  The only time I've worked with companies who have had anything close to a decent expierence with portals, they're either not big enough for their small number of portals to matter, or they're a highly technical developer who has a good understanding of _exactly_ what is going on under the hood and how portals really work.