Actually, the term "axis" has very specific meaning when used in discourse these days: it is intended to draw a direct line back to Hitler's Germany, seen by many as the ultimate expression of evil (although in a historical sense that's debatable...there are many contenders for that throne). Prior to this, the term wasn't in common use at all. Alliances were alliances, either of convenience (as might be seen with France and Russia prior to World War I or the US and USSR during World War II) or out of ethnic ties (see Germany and the Austro-Hungarian Empire prior to World War I). There was not an implied linkage "to the death" or automatic connotation of evil...until ol' Benito coined the term "Axis."

While Iran and Syria may have some common goals and objectives, I think it's rather foolish to automatically assume that they are joined at the hip in evil intentions. Alliances in the Middle East historically tend to be very fluid things, used and discarded as convenience dictates (this can also be said for much of the world). Describing them as an Axis carries a specific message...one that I believe is intentional on the part of those using the term.