TipJar LLC would like to follow the model of a physical tip jar and not be concerned with facilitating the Tax Man. In reality, working with a database means never forgetting where the money went.
My reading of the regulations about 1099 forms means that it is up to the individuals involved to report their own income, when a employer pays a contractor $600 or more over the course of a year. To make this easier, each year on January First I'll send out annual summaries to everyone.
Since I'll have the information handy in the database, I may have to report any pairs of tipjar accounts where one has given the other more than $600 US Dollars during the year to the IRS. When this happens I will certainly notify the parties involved that they have gone over the $600 limit and are being reported. It will be noted on your annual summary.
For non-U.S. Dollar currencies, having a clear taxation threshold policy will be the responsibility of the liaison for that currency, and implementing it will be a part of the negotiation prior to the currency's availability in TipJar transactions.
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News article about U.S. internet sales tax legislation