First let's get some perspective on the sums involved. One of the tip4commit spams I got after a commit informed me that my tip balance was 0.00000171 BTC. At current exchange rate this is equivalent in US dollars to $0.0005525523.
In other words, at a rate like that, it requires nearly two thousand tips just to add up to a single US dollar worth of tips.
And it gets worse. Remember that tip4commit "refunds" the tip back into the project pool if it's not claimed within 30 days. So just to get money out of this, you have to be making enough in tips, every 30 days, to overcome the cost in both time and potentially transaction fees of claiming the tips.
And then you have to do a bit more figuring to see if the money you'll get once cashed out is enough to justify the bookkeeping cost it imposes on you; after all, now that's income that you need to keep records of and figure into your taxes, which is not a zero-cost thing.
So first of all, you need to figure out the expected amount of tips, both over rolling 30-day periods and over the course of a year, which again is not a zero-cost thing, since if nothing else it involves spending time, and calculate whether they are enough to overcome the friction of getting the money out of tip4commit and then the cost of keeping records of and reporting it.
It is highly unlikely at this time that any person will be earning enough in tips from tip4commit to reach the point at which it becomes profitable even to the tune of a few units of local currency. A final data point for this: tip4commit states that it tips out at 1% of the balance of the project on each commit. Its attempt to tip me 0.00000171 BTC was for a commit on Django, which means the balance of donations for Django at that time was 0.000171 BTC, which simply cannot be enough to make it worth while for any person who contributes code to Django. And I don't rate it likely that there are a bunch of other projects with balances significantly larger, which means it is probable that there is currently no individual developer in the world for whom accepting tips from tip4commit is a profitable activity.
And that's without getting into the problems associated with the site displaying your name in tipping lists even if you never accept them, or the problems associated with displaying projects -- quite a few large open-source projects have associated non-profit foundations, and are bound by law regarding donations made for specific directed purposes. Although you can argue it's unlikely any person or organization would ever actually be punished based on tip4commit listing them, it certainly is possible that they could be called upon to prove that they are unaffiliated with tip4commit and refuse to accept the tips. Which, once again, is not zero-cost; now it potentially costs individuals and projects time and/or money for something they had no control over because tip4commit "opted" them in forcibly and continues to drag its feet on opt-out.
All in all, this is a mess. It probably should just shut down, but if it stays operating it's going to keep getting heat, and will keep deserving it, until it switches to being based only on explicit opt-in.