Does the FAA verify or authorize VFR flight plans?
First, one small clarification: ATC doesn't offer any services to an aircraft on a VFR flight plan unless you call and request them.

This short Ask ATC video from AOPA has some useful comments:


Controllers don't know anything about your VFR flight plan
VFR flight plans are for search and rescue purposes only
Even if you call ATC and request flight following, they only enter the destination into their system, not your route (I assume that's because your route could be 'follow that river and then that interstate')


The key point is that VFR flight plans are recorded and managed by FSS, not ATC. So, does FSS accept whatever they're given? I couldn't find a direct answer to that question, but the FAA's procedures for receiving and handling VFR flight plans (see Chapter 6) don't include any steps to "validate" the plan (whatever that would mean anyway). Although there's a lot of detailed, tedious information there so I may have missed something :-)

In fact, this AOPA explanation implies that no one even looks at the route unless it's as part of the SAR process:


  ETA plus one hour
  
  Within a half-hour of becoming overdue or at ETA plus one hour, the
  search is widened by sending an INREQ (information request) to flight
  service facilities along the route (which is why the route of flight
  is specified on the flight plan). If [the pilot] had been on an IFR flight
  plan, the INREQ would have gone out at ETA plus 30 minutes.


The bottom line seems to be that no one really cares about your VFR flight plan unless it's actually needed to find you. So even if you can enter a nonsense plan, it wouldn't be a very good idea.