Quote from: empoweoqwj on January 09, 2014, 10:30:16 AM

Do people actually make money at cex.io? If so, hard to argue against market forces. If not, what the heck are people doing???

Lets look at this historical data I got from cex.io thread

Quote from: JayBee66 on January 08, 2014, 02:26:05 PM

These are the closing prices from October 1st to December 27th. Others may fill in the gaps.

1-Oct    0.23000000
2-Oct     0.23849000
3-Oct     0.23000000
4-Oct     0.23510000
5-Oct     0.22400000
6-Oct    0.21000000
7-Oct    0.21790000
8-Oct    0.21730000
9-Oct    0.21700000
10-Oct   0.19120000
11-Oct   0.18990000
12-Oct   0.18478000
13-Oct   0.18180000
14-Oct   0.18270000
15-Oct   0.14250000
16-Oct   0.13399900
17-Oct   0.13998000
18-Oct   0.14039900
19-Oct   0.14131000
20-Oct   0.13890000
21-Oct   0.13180000
22-Oct   0.12200000
23-Oct   0.09500000
24-Oct   0.08266000
25-Oct   0.09090900
26-Oct   0.09750000
27-Oct   0.09980000
28-Oct   0.10427500
29-Oct   0.10410000
30-Oct   0.10600000
31-Oct   0.10748900
1-Nov   0.10760900
2-Nov   0.11046900
3-Nov   0.11999900
4-Nov   0.10050000
5-Nov   0.10710000
6-Nov   0.11411900
7-Nov   0.10517900
8-Nov   0.10189900
9-Nov   0.09445000
10-Nov   0.09638000
11-Nov   0.09582600
12-Nov   0.09110000
13-Nov   0.09099900
14-Nov   0.08100000
15-Nov   0.07920000
16-Nov   0.07990000
17-Nov   0.08097900
18-Nov   0.08074000
19-Nov   0.07866000
20-Nov   0.08402000
21-Nov   0.08205000
22-Nov   0.08199900
23-Nov   0.08400000
24-Nov   0.08499900
25-Nov   0.08661100
26-Nov   0.07974000
27-Nov   0.07680800
28-Nov   0.06767000
29-Nov   0.06599900
30-Nov   0.06879500
1-Dec   0.07150400
2-Dec   0.07128873
3-Dec   0.07210000
4-Dec   0.07308999
5-Dec   0.07399962
6-Dec   0.07986940
7-Dec   0.07699900
8-Dec   0.07555444
9-Dec   0.07237200
10-Dec   0.06949988
11-Dec   0.07118001
12-Dec   0.07389989
13-Dec   0.07397213
14-Dec   0.07346848
15-Dec   0.07189998
16-Dec   0.07257734
17-Dec   0.07232347
18-Dec   0.07187850
19-Dec   0.06999992
20-Dec   0.06769040
21-Dec   0.06861000
22-Dec   0.06795171
23-Dec   0.06239999
24-Dec   0.05619993
25-Dec   0.05664157
26-Dec   0.05127993
27-Dec   0.04988691

I dont use cex.io so I cannot say if it is profitable or not but lets do a simple math using the data above.

Say you got 10ghs on 5th Nov 2013 at 0.10710000btc/ghs totalling 1.071btc.
You let it mine for a month with difficulty 510929738 and got 0.2953btc. I assumed the difficulty does not change so the amount will be less than this.
Then on 5th Dec 2013 you sold your 10ghs at 0.07399962 totalling 0.7399962btc/ghs.
Your profit will be .7399962 + 0.2953 - 1.071 = -0.0357038btc.

I picked the date at random and data for difficulty I got from http://bitcoinwisdom.com/bitcoin/difficulty
It does not look like a good investment to me. You could increase your btc holdings by daytrading but I wouldnt call daytrading an investment.