yes it can happen, chicago: people who have Certified you, who are "closer" by degrees to the top-level seeds than you, happen, in your absence, to also Certify other people.
then, the "max flow" algorithm "diverts" flow through those people, leaving not enough to "flow" through your "node".
what is supposed to happen is that as the number of people in the database increases, so is the "maximum capacity" of each "degree" supposed to be increased, in order that more "flow" can reach more people.
that, however, requires a recompile of the c source code mod_virgule.c.
mod_virgule has not been actively maintained since it was written, nearly six years ago.
p.s. i understand the theory, design and implementation behind the mod_virgule code very well, having done a complete rewrite into something called xmlvl (xml virgule language - before zope, dtml and xslt were well-known) and also a port of the trust metric algorithm to python.
p.p.s. lack of disk space on the advogato server(s) has in the past resulted in truncation of people's profiles. i've lost nearly a hundred Certs from other people at least once.