Ever wondered what private BitTorrent tracker sites are the hardest to get into? Well, with a little assistance I've been able to compile a list of what BitTorrent tracker sites have the distinction of being the most exclusive.
Now I've tried to display the data without giving too much of a heads up to "the man," so I have purposefully left off the complete domain names and in some cases left the name to be determined by those "in the know" with the help of a few asterisks.
Here private BitTorrent tracker sites are rated on a scale from 1 To 5, with 1 being the easiest tracker site to get into, and 5 being the the hardest. Note that it has nothing to do with the type of content available on the tracker sites, merely the ability to gain membership, i.e. invited. I have purposefully left out content rankings so as to avoid making any of the sites a target for any copyright enforcement action.
Also to note: THIS LIST SHOULD NOT BE TAKEN LITERALLY. It's just to explain where each site stands in terms of signup or invite availability (rarity-wise), and please, DO NOT ASK for the exact URL for any of the sites specified in this story. If you're a legitimate member of the BitTorrent community you should have no problem finding them out on your own.
LEVEL 1
These sites are pretty much always open for signups .Those looking to join can register at almost any time.

Bitsoup - ILoveTorrents - Midnight Torrents - docs.torrents.ro - DVDseed and countless others...

Level 2
Invite for these sites are fairly easy to obtain. Chances are you will be able to get one for free from a freind or an acquaintance.

Pisexy - Demonoid - TL - iPLAY - ST - SCC - FileZone - FL - DH - HT - ChronicTracker - TD - SITR - XboxSky - PussyTorrents - Dimeadozen - Bitspyder - Filemp3 - Learnbits - HorrorChannel- KrayTracker - TVJunkies - UKNova - Elbitz - TvT.ro - BitHDTV - x264 - FinDVDR etc.

[2.5]

RevTT - TTi - TorrentBits - WB - TauriTracker - TB - SoftTorrents - PotUK - A-L - TVTorrents - Audionews - BlackCats - TheVault - ProAudioTorrents - CO- Brokenstones - AOM - Music-Vids - ExtremeBits - BTMusic - Goem ...etc.

Level 3
These sites are also fairly easy to obtain but, you won't be able to get one for free in most cases. They aren't so easily doled out and you will most likely have to offer an invite to another site in return.

Swebits - Snowtigers - BitMe - OiNK - KG - ThePlace - HDBits - VIPMusic - RMVBusters - - Sweloaders - TS-Tracker etc.

[3.5]

FSC - Thor'sLand - RP - CZone - PT - Danishbits - rSR - BitMeTV - IT - etc.

Level 4
These sites are harder to obtain invites to for various reasons, though it is possible provided that you offer a similarly ranked site in exchange.

NB - SweDVDR - TT - Revolt etc.

[4.5]

FB - FTWR - E***o etc.

Level 5
Getting an account at these sites is very difficult if not impossible to do. Consider yourself very lucky if you have an account at one of these trackers sites.

FTN - ScT and U***

Stolen from Zeropiad