Are programs like CleanmyMac2 safe to use

Question

Are programs like CleanMyMac2 a good thing to use or they unnecessary?

Answer 1

They are neither good nor necessary. Save your money.
Kappy's Personal Suggestions About Mac Maintenance
For disk repairs use Disk Utility.  For situations DU cannot handle the best third-party utility is: Disk Warrior;  DW only fixes problems with the disk directory, but most disk problems are caused by directory corruption. Drive Genius provides additional tools not found in Disk Warrior for defragmentation of older drives, disk repair, disk scans, formatting, partitioning, disk copy, and benchmarking. 
Four outstanding sources of information on Mac maintenance are:
1. OS X Maintenance - MacAttorney.
2. Mac maintenance Quick Assist
3. Maintaining Mac OS X
4. Mac Maintenance Guide
Periodic Maintenance
OS X performs certain maintenance functions that are scheduled to occur on a daily, weekly, or monthly period. The maintenance scripts run in the early AM only if the computer is turned on 24/7 (no sleep.) See Mac OS X- About background maintenance tasks. If you are running Leopard or later these tasks are run automatically, so there is no need to use any third-party software to force running these tasks.
If you are using a pre-Leopard version of OS X, then an excellent solution is to download and install a shareware utility such as Macaroni, JAW PseudoAnacron, or Anacron that will automate the maintenance activity regardless of whether the computer is turned off or asleep.  Dependence upon third-party utilities to run the periodic maintenance scripts was significantly reduced after Tiger.  (These utilities have limited or no functionality with Snow Leopard, Lion, or Mountain Lion and should not be installed.)
Defragmentation
OS X automatically defragments files less than 20 MBs in size, so unless you have a disk full of very large files there's little need for defragmenting the hard drive except when trying to install Boot Camp on a fragmented drive.
Malware Protection
As for malware protection there are few if any such animals affecting OS X. Starting with Lion, Apple has included built-in malware protection that is automatically updated as necessary. To assure proper protection, update your system software when Apple releases new OS X updates for your computer.
Helpful Links Regarding Malware Protection:
1. Mac Malware Guide.
2. Detecting and avoiding malware and spyware
3. Macintosh Virus Guide
For general anti-virus protection I recommend only using ClamXav, but it is not necessary if you are keeping your computer's operating system software up to date. You should avoid any other third-party software advertised as providing anti-malware/virus protection. They are not required and could cause the performance of your computer to drop.
Cache Clearing
I recommend downloading a utility such as TinkerTool System, OnyX 2.4.3, Mountain Lion Cache Cleaner 7.0.9, Maintenance 1.6.8, or Cocktail 5.1.1 that you can use for periodic maintenance such as removing old log files and archives, clearing caches, etc. Corrupted cache files can cause slowness, kernel panics, and other issues. Although this is not a frequent nor a recurring problem, when it does happen there are tools such as those above to fix the problem.
If you are using Snow Leopard or earlier, then for emergency cleaning install the freeware utility Applejack.  If you cannot start up in OS X, you may be able to start in single-user mode from which you can run Applejack to do a whole set of repair and maintenance routines from the command line.  Note that AppleJack 1.5 is required for Leopard. AppleJack 1.6 is compatible with Snow Leopard. (AppleJack works with Snow Leopard or earlier.)
Installing System Updates or Upgrades
Repair the hard drive and permissions beforehand.
Update your backups in case an update goes bad.
Backup and Restore
Having a backup and restore strategy is one of the most important things you can do to maintain your computer. Get an external Firewire drive at least equal in size to the internal hard drive and make (and maintain) a bootable clone/backup. You can make a bootable clone using the Restore option of Disk Utility. You can also make and maintain clones with good backup software. You can never have too many backups. Don't rely on just one. Make several using different backup utilities. My personal recommendations are (order is not significant):
     1. Carbon Copy Cloner
     2. Get Backup
     3. Deja Vu
     4. SuperDuper!
     5. Synk Pro
     6. Tri-Backup
Visit The XLab FAQs and read the FAQs on maintenance and backup and restore.
Always have a current backup before performing any system updates or upgrades.
Final Suggestions
Be sure you have an adequate amount of RAM installed for the number of applications you run concurrently. Be sure you leave a minimum of 10% of the hard drive's capacity or 20 GBs, whichever is greater, as free space. Avoid installing utilities that rely on Haxies, SIMBL, or that alter the OS appearance, add features you will rarely if ever need, etc. The more extras you install the greater the probability of having problems. If you install software be sure you know how to uninstall it. Avoid installing multiple new software at the same time. Install one at a time and use it for a while to be sure it's compatible.
Additional reading may be found in:    
1. Mac OS X speed FAQ
2. Speeding up Macs
3. Macintosh OS X Routine Maintenance
4. Essential Mac Maintenance: Get set up
5. Essential Mac Maintenance: Rev up your routines
6. Five Mac maintenance myths
7. How to Speed up Macs
8. Myths of required versus not required maintenance for Mac OS X
Referenced software can be found at CNet Downloads or MacUpdate.
Most if not all maintenance is for troubleshooting problems. If your computer is running OK, then there isn't really a thing you need to do except repair the hard drive and permissions before installing any new system updates.