Regarding performance, I get the same headache as NaquadaServ. Spiritfire3292 will not misuse such an event but, to be sure, many people out there will.
Think of While-Loops using global vars, or ppl not using a (fictive)
Code:
on *:var: {
 if (($1 == v.name) && ($2 > my.limit)) { stuff }
}

but
Code:
on *:var: {
 if (stuff isin $1) { triggering stuff }
}

or even
Code:
on *:var: {
 if (($hget(vars.to.watch,$1)) && ($2 // $ifmatch)) { stuff }
}

and what about things like
Code:
on *:var: {
 ...
 while ($2 > limit) { set $2 another lower value }
}

etc ? (just thinking aloud) Well, it might be a desirous event, anyway smile