If something like that went to trial you need witnesses in person along with expert witnesses who can explain Bitcoin. Then, even if you get a judgment, you still need to collect it.
http://en.wikipedia.org/wiki/Digital_evidenceIt's not necessary to bring the nature of Bitcoin into a breach of contract action - in fact, if you read the California action filed in respect of Bitcoinica you'll notice that they've been careful to avoid making the nature of Bitcoin an issue and kept it about the USD value owed.
What
might be an issue is people not having acceptable proof of their transactions. If Tom has adequate records, this shouldn't be a problem. If he doesn't, though, it's much more difficult to obtain independent evidence relating to the transactions than it is with bank, CC or PayPal transactions where a disinterested third-party can provide information relating to the transactions.