The table is not fragmented when it has double digit extents.

There are some issues with very high numbers of extents, but that is more to do with the dictionary tables and how the default cluster key size is not set up to handle very high no. of extents in many tables.

A good followup on this issue would be to look at the asktom.oracle.com site and search on the topic or
http://www.ixora.com.au where Steve Adams also talks about the issue.

Both basically debunk the idea that tables should be in one extent.

Have Fun