That is true, but there's still a Right Way and a Wrong Way. The Right Way (aka the Debian Way) is that if you create a repository to put your application in, then any dependencies are to be resolved by either
a) keeping the dependencies in the same repo (i.e. anything in the repo that needs some library will find the library in the same repo).
or
b) dependencies can be resolved by packages in the "core" repositories, which for the N800 would be the Nokia catalogue repos, and would in practice probably also have to include repository.maemo.org, but then that repo should have been in the default list on an N800 fresh from the box.

The N800 (and 770) repos are unfortunately to some extent set up the Wrong Way, that is, dependencies have to be resolved by hunting down an awful lot of repositories until you find the obscure one that has what some application in another obscure repo needs. This situation should be easy to clean up.