I seriously doubt it, there is almost certainly something else going on. Does the dropbox api even use udp at all? A udp flood has little to do with the size of a file transfer, and everything to do with the rate of udp packets per second. Generally to be identified as a "flood" your server would have to be doing something very poorly coded (best case) or downright malicious. Did you check where this udp traffic was being sent to (destination ip addresses/ports)? Did you compare the dates/times of the "flood" to when your scripts/jobs were running? Did you check your server for any suspicious activity or indications of compromise? A little bit of critical thinking can go a long way here.

10MB once no, but lets say hypothetically, if the dropbox api returned an error or wasn't available which denied your request but your script didn't account for it and it constantly kept making the request over and over and over. The 10mb would soon add up.

Also, are you sure it wasn't something else, not the dropbox db script which could have caused problems?

What about the crawling? How much traffic does that generate? I'm just wondering if you are hitting one or more of the sites very hard and they complained to DO about it.