yesterday I put a new battery in my bike because it died and a new solinoid in it because it was on the way out. Later that afternoon I washed it and poured a bucket of water over it to rince it off. At 1 in the morning Im woken buy what sounded like some loud mechanical noise then I realized it sounded like my starter motor on my bike I rushed outside and it was sitting in the shed just turning over and over.The battery was dying and smoke was coming off the solinoid.I had to find a allen key and unscrew the seat then unhook the battery. In the morning I had a look over it and found that the starter button ( which is a horn button rivited to the frame) had shorted out inside. So even when the bike is turned off the starter button will turn the bike over but it wont start because the starter motor wiring comes straight off the battery and not through the main on switch.I think that maybe the bucket of water might have caused it or it was just on the way out.I have ordered a new button which I will wire through the main ingnition set up.

yes sparra I will be doing that its lucky it wasnt in gear or something like that. I was so freaked out I got up at 2am to check. I dont no what the neighbors thought its close to their bedroom.

I have seen a few bikes that have gone "clang" when you turn the key on, as a little moisture was present in the switch, that caused a momentary operation of the starter.
So the water really is a likely cause(catalyst).
I can only assume that the switch (in this case a horn type button) was connected directly to the solenoid, as opposed to a relay, which(ultimately) resulted in the switch failing(somewhat unrelated to the starter coming on).
I do not know why people eliminate relays, as they are very effective and reliable(and cheap).
A fuse would be a waste of time. If it is rated to survive normal operation, it will not blow unless there is a short(and there wasn't, just an under-rated switch). If the fuse is rated to blow before the switch, then it will blow during normal operation, which would be no fun at all.
The solution, of course, is to run a relay, and only have the button live after key(as previously stated). Naturally, the feed to the starter button will be protected by the ign circuit breaker anyhow(as it should be fed from the kill switch). And if you do not have a kill switch, you should get one. Also cheap, and reliable, and may help you avoid crashing into people, and killing their children(and us other road users would appreciate that).

yes I will add a relay and yes I have a kill switch.