As Rob said, the Titans have pretty sophisticated tools to investigate this stuff once they have a list of accounts to start looking at, but if they don't get any tips on where to look, it's not easy to figure out where to start.
You're not going to get penalized if the Titans decide they aren't multis, either. People who are working to try and make the game better are appreciated, even more so if they go through the proper channels 
Have the titans gotten less lazy? Last time I pointed them to very fishy people, they just shrugged and basically said "Meh, you didn't provide conclusive evidence" and closed the issue.
