It seems to me that most people posting on this thread are completely clueless about how things work in that region of the world, especially when it comes to Turkey. So let's get some facts straight:
1) What the pair of Turkish RF4's were doing in Syria, is what they are doing practically every other day over Greek (or Cypriot) air defenses, i.e. getting as close as possible to photograph installations of interest. Anything else you hear about what they were doing (e.g. "testing Turkish air defences and accidentally straying in Syrian air space " is a bunch of Turkish hogwash. If you believe that, I have a bridge in Bosporus to sell you, and you are probably too naive to understand geopolitics and should refrain from reading further - period.).
2) In this case, the pair of RF4's got REALLY close, trying to test the Syrian AA defences in order to assess the feasibility of setting up a NATO-imposed no-fly zone (a la Libya), and/or photograph the Russian installations especially with regards to the P800 Yakhont supersonic anti-ship missile (in case of imposing a naval blockade on Syria)
3) The pair of RF4's were flying no more than 2 to 3 miles from the Latakia coast (some sources say even less, 1-2 km), at low speed (no more than 500 mph) and low altitude (5000 ft). The largest piece from the wreck of the RF4 (a tail section) was found only 2 miles from the shore.
4) The RF4's were engaged with AA cannon fire. They were not engaged with SA-5, S-300, or any other missiles. END OF STORY. One RF4 was brought down and the other made it back to Turkey with apparently little or minor damage.
5) The question is what AA fire brought the RF4 down. There are two candidates: the ZSU-23mm or the Pantsir S-1. Evidence points out that the RF4 WAS TRACKED BY AND BROUGHT DOWN BY CANNON FIRE FROM the Pantsir S1's 2A38M 30 mm autocannon guns. This is supported by the best detective work on the subject, carried out by the greek defence website, defencenet.gr, in which they compared the sound from the cannon fire from the amateur video of the incident, with cannon fire from the promotional video of the Pantsir S1 firing its 30mm autocannon. The sound is exactly the same (and different from ZSU-23mm cannon fire). This damn website will not let me post links to this so please search for it.
6) If you have a better theory with corroborating evidence I am all ears, but please do not insult my intelligence with official Turkish statements.