But what you said above is interesting, for you the acceptable limit of a shortened address should be 10 characters at least.
I see no point in shortening anything. It requires trusting a third party, while I'm using Bitcoin so I don't have to.
Address strings shorter than that are such risky? I mean 7+ characters is not enough according to you? Are there some figure (stastistics) about that somewhere?
I did a quick check of currently funded addresses. These are the most common "firstbits":
533 13vs7FtkinfdQEr
178 1MRQMyG8NXuWy8Q
114 111111111111111
100 18mUfVHHPB719p5
69 15PoAPLdagVwbrm
51 16r4jPvxVavBnYn
51 15DBQVf9USmepuX
42 1GQbCRKfSpv61Aw
41 19nbKmgGAMztCiY
40 19UjqqjXmQxyyn4
38 19yZWbp6CkYbRgy
38 13vs7FtkinfdQFN
36 1B4fGbLPqKwVYMU
36 14WCuwmL7JVDe53
35 1GameWinnerSide
26 1ML7gn8oxMfpSap
26 19wBDoN7rJ9UcW2
26 19QStptbvStgmpk
26 16r4jPvxVavDRkq
25 16fVWdPe5SnALYv
25 13xUrWtr33gisFr
24 1Nt1B3HD3MghPqr
24 1AJKvZsPX16GigP
24 16VFGgrSaoLKvPr
24 16QBpnaoAz1Xs6b
23 16m7JGEPqL3RW2d
23 13vs7FtkinfdQFM
22 1EQGLCYgGwiiRBx
22 16aF7KsfBdmjvgu
22 16Jswqk47s9PUcy
22 157sXYpQRKuWSRu
21 18bNsPWJ9aGbamJ
21 183jdoiA97a8qfk
21 14hoiMjKhVBwrTG
20 1BXPA1djHX35pz9
20 1B4e3UJDK5Vkeiy
20 14Cnk6Qyt9G4Zfh
19 1uskvGBAmMzGa4p
19 1PtAc9fhdJHPBqM
19 1FpRnXcCcX3ywVE
19 18bNsNXERj1h3KD
19 16fpd575R9oiyV2
19 161pAYwTvhzRy5d
18 1KsWsi7jHXte1sN
18 1DagSW5akR6P1P4
18 1BXPA1djHX35pyz
18 1BEV752mACUZvEA
18 1BERYJqWFpuYkQR
18 18QcRiTePyNthuY
18 1888b6fTnxeNqZ1
18 17KTE2wt487iCPX
18 17KGeeW7k4JTzv5
18 147ShXWnUXq3WSg
18 13wvPzKvNwJH9bb
17 1wCaSFw7UjGQFJ3
17 1CKeWxvmG6T3dFd
17 18bNsPCTrsW4fSH
17 17JFawv7Wre64YK
17 16WFtzRtaYpWtyt
17 15JWVCDKAWGF5KB
17 14r57Eaj5d5kSbE
17 147mhhaBkDCAEEW
17 147SoGcj4pHywAg
16 1h8BNZkhsPiu6EK
16 1MhGPYe5d4ccYmB
16 1K9DUB7Bx813oWe
16 1HKTxLaqcbH5Gcq
16 1DbWv9gqxSEdDd5
16 1BRsWDnXk6N5vbr
16 1AXGKL9ZWaxBUBa
16 1A7kaBckgecsfbC
16 18W1PkAxT3giXpu
16 16PkuZhrvF2zyqr
16 147UrgQxdJD25hX
16 13BuDc2d1EfmeCL
16 12rRrC5QCh1Ncp2
16 12Bx3iADamGzzvB
15 bc1qghzja3vxyzp
15 1Jgn6DUbsEpZAnh
15 19rZPxyNUcvPN7e
15 18bNxYyP6tSEmov
15 18bNsPKbaMQgENH
15 17W7Xt5cDCkQYdP
15 16WKqFnuw4dKhYx
15 12rQMgNAMF6URj8
15 12pkttrsneitCKz
14 bc1qysgu4uneqzp
14 bc1qtanrvt8jywc
14 bc1qjkjy6y7eer0
14 bc1qgs8z5x3ezsq
14 bc1q8ena4prt3sx
14 1viSGjrKU19VsHe
14 1QFKJvAyJ1EBJ1i
14 1L46E6NN7tN34xZ
14 1Fb17hBohEnoGGd
14 1DVPaHHW7BMj9k3
14 1CaWpN2KwQzjtJ9
14 1BDCgV8ZgmTFz8H
14 1AEJUzcZoCJ85Ra
14 19a2X2rrBbCgWKf
14 18J2aaSW9btXnJx
14 188888888888888
14 15NoSD4F1ULYHGW
14 13xMkEYshcCWH1E
14 114MiTMoanBtHJe
13 bc1qz3l4l4gag7j
13 bc1qymlykkjex0r
13 bc1qyl66nv06t06
13 bc1qvvme2zmdrds
13 bc1qpms8f82hkv9
13 bc1qp0zms4q8agv
13 bc1qmzdh66t2dk9
13 bc1qldcu87xr9le
13 bc1ql2yzwqsmelt
13 bc1qjfd5sy2g848
13 bc1qj3k3mvzl0xt
13 bc1qfng24nqthrc
13 bc1qed498rk2e9n
13 bc1qdztlktdghjm
13 bc1qd8uxf384kyn
I think many of them are burn addresses, but that can be done to any other "firstbit" address too.