How does tone sandhi apply in people's names?
The rule that applies to sentences also applies to names, that is for a sentence of sequential 3rd tone characters,


(Optionally) Split it to phrases by functional groups.
For each group, every other character is read as 2nd tone while keeping the last character 3rd tone. 

2.1. If a group has even number of characters, the tones become 2,3,...,2,3,2,3.
2.2. If a group has odd number of characters, the tones become 2,3,...2,3,X,2,3. If the group has exactly 3 characters, it becomes X,2,3. In standard Mandarin, X=2. In spoken language you'll probably hear both X=2 and X=3.



Examples:


马友友: 

223: ma2 you2 you3 (standard as you'll hear in CCTV news).
323：ma3 you2 you3 (colloquial).

similarly, 往北走: 

223: wang2 bei2 zou3 (standard).
323: wang3 bei2 zou3 (colloquial).

领导很满意: 

2323...: ling2 dao3 hen2 man3 yi4.

往北走也挺好. Both of the following are correct:

223 223: wang2 bei2 zou3 ye2 ting2 hao3 (rule is applied to 2 word groups respectively).
232323: wang2 bei3 zou2 ye3 ting2 hao3 (rule is applied to the complete sequence).

请你老叟往北走. (This is a well-known line in TV/movie industry for tone sandhi practice, similar to 八百标兵奔北坡 for stop consonant practice.)

2323223: qing2 ni3 lao2 sou3 wang2 bei2 zou3.