Other sites get paid to do so. We do it pro bono.
Well maybe Nalicity has other problems that go beyond technical. Maybe you just need a better business model.
Free information on the internet is a dying concept, and it's pretty obvious that if you want something good, you're going to have to pay for it. What if you relaunched the website with basic services for everyone, but left certain functions to paid members. For instance, along with the MoTM, and Hotlist, you could have an area on the front page where authors could pay a minimal fee to keep their map viewable on the main page. For those users who just come here to download, maybe limit their number of downloads per day or leave advanced search functions unavailable unless they become registered, paid members.
I'm not saying restrict any of the content, because I believe that authors who publish their maps here come here to do just that. They want everyone to enjoy what they have created and in no way am I encouraging the site to block that. However, adding perks for a small fee might offset some of the costs of maintenance. I'm not suggesting that the site administrators should get rich (and I expect the reviewers to still be unpaid volunteers), but some income is better than no income, and there WILL always be people more than happy to shell out money for something they love. And I know alot of people absolutely love what Nalicity did for the UT community.
IMO free stuff is actually super popular these days, and people expect everything to be free online, more than ever. The huge rise in open source software is an example of that.
The whole point of a community is that it is a free, and easily accessible by everyone.
Look at Fileplanet and similar. They want me to pay so I can download a free file faster. Am I going to pay then? Hell no, I just look for another download location that is fast AND free.
We would only lose members like that.