A lot has been said and published on the topic of segmentation, typology or cluster analysis. One possible reason for this activity is that the approach is very plausible and even simple at the first glance. On the one hand the concept of "type" is well known in everyday language (e.g. "a modern type") and on the other hand, even the mathematical (numerical) part of this approach seems to be rather simple at the first view: one only has to find homogenous groups of objects (e.g. persons) that are maximally separated. This paper will snow that there are a lot of difficulties in the realisation of clusterings and give some hints for finding acceptable solutions.