That's essentially it, a substantial difference -- every running service
on a smart phone is a point of vulnerability.

There's no need for major hassles when J2ME applications are programmed
properly -- it's not all or nothing -- different security options exist.
That said, it's a major vulnerability to allow apps to access data like
that.

I've used both, and don't see any significant usability issues with
"just" J2ME.

The risk comes from allowing things that create points of vulnerability.
It's the same naivete that got PC versions of Windows into so much
trouble.

Again, smart phone viruses do exist, and it's only a matter of time
until they get to be a serious problem.

That's hardly reassuring.  But suit yourself -- I'm not interested in
taking such risks for no good reason.

"Embedded devices a cinch to pwn"
<http://www.theregister.com/2007/04/19/embedded_devices_security/>

  Cell phones, modems, routers and similar devices are a lot easier to
  hack than most people think, making them an opportune target for
  criminals looking for an easy way to pierce a network, a researcher
  from Juniper networks says.

  Speaking at the CanSecWest security conference in Vancouver, Barnaby
  Jack demonstrated how a soldering kit and some basic knowledge about
  the processors typically used in embedded devices can allow
  miscreants to download the firmware running on the hardware. The code
  can then be modified to make the devices do all kinds of nefarious
  things, he warns.

  Over the past decade, computers - usually those running Windows -
  have emerged as the vector of choice for cyber crooks. That is
  beginning to change for several reasons. For one, years of trial and
  error (with an emphasis on error) has helped Microsoft harden the
  defenses of its software, making it harder to find critical
  vulnerabilities. At the same time, the number of cell phones, routers
  and other embedded devices has proliferated.

  Hardware designers often make it easy for their devices to be hacked
  because they contain debugging functionality and hardware interfaces
  not needed by end users.

  Jack demonstrated how modified firmware for a router made by D-Link
  changed default settings so remote administration was enabled. (He
  emphasized gear made by other vendors was equally at risk.) That in
  turn would allow the router to be accessed remotely, potentially
  allowing the altering of DNS settings or the disclosure of VPN
  credentials.

  We would have been more impressed had it been possible to modify the
  firmware remotely. Alas, that was not the case. To alter the
  settings, the criminal would need to access the device on the local
  area network. Jack claims similar attacks could be carried out over
  the net.

  We'll give Jack the benefit of the doubt here, not just because we're
  in a charitable mood, but also because he makes a good point.
  Embedded devices are everywhere and we suspect little thought or
  money is put into fortifying them against the increasing
  sophistication of today's cyber attacks. Consider yourselves warned.