The limit of 2 PM per day is set for a reason, that to make spamming more difficult, as theymos said, and for those type of deal that involve escrow you can always do them in public,
Looking into it, it looks like they can get 5 PMs per hour, can you tell me where you got this other information?
--snip--
what you quoted is outdated, here is the current limit
| Activity | Max recipients | Max recipients if whitelisted | Max PMs per hour | Max PMs per hour if whitelisted | Max PMs per day | Max PMs per day if whitelisted |
| 0 | 2 | 10 | 1 | 40 | 2 | 120 |
| 15 | 3 | 10 | 10 | 40 | 15 | 120 |
| 30 | 5 | 10 | 10 | 40 | 30 | 120 |
| 100 | 7 | 14 | 20 | 80 | 150 | 600 |
| 250 | 15 | 30 | 120 | 120 | 300 | 1200 |
| 500 | 30 | 30 | 120 | 120 | 1200 | 1200 |