SolrDocument serializable?

[Ryan McKinley]

How do you all feel about forcing the fields in SolrDocument to be  
Serializable?
from
  private Map<String,Object> _fields = null;
to:
  private Map<String,Serializable> _fields = null;
likewise with SolrInputField?
from:
  Object value = null;
to
  Serializable value = null;

Everything we are pumping into these fields is serializable.  The only  
catch is that List/Map are not Serializable, but the implementations  
we use are.

thoughts?