Among eccie PMs, text messages and voice calls, the text messages are the most risky in my opinion, then followed by PMs, and with voice calls being the least risky.
Why? Long answer follows for the skeptics. My opinion--others may differ.
First, the interception of voice calls requires LE to show probable cause to get a wiretap warrant through a judge with strict controls on what can be recorded. In my experience, they normally only do this for big cases, national security, and organized criminal activity--more than just an individual john setting up a single appointment with a provider. If they want to go back and see who you have been calling, all they can collect are call-detail records. Phone companies have strict rules and processes place to ensure this voice interception and call-detail records not abused by LE, or by phone company employees trying to do a friend a favor.
The collection of voice call-detail records would require LE to show probable cause to get a warrant for your telecom carrier records. Voice call detail records normally are available for each and every call to/from your phone for approximately 60 days as normal business any by government regulations. It may take several days to weeks for this information to be provided. Governments bureaucracies dealing with phone company bureaucracies--but it can happen fast in emergencies or exigent circumstances when lives are at stake--paper work then follows.
You may wish to check the on-line records of your phone via your phone company web page to see how far your personal billing records go back. These records do NOT contain voice call content, but simply show who and when you have been communicating. There may be some location information about where your cell phone was located when you used it. They may also be able to track the location of your phone in the past. All of these call-detail records are routinely requested by divorce lawyers as a happy hunting ground when building a case against a wayward spouse.
LE and divorce lawyers still have to get a legal subpoena to require the phone company to turn over the records. The phone companies will then bill the lawyer and LE for the reasonable costs to maintain, obtain and assemble these records--not cheap so LE normally does this only for bigger cases. Divorce lawyers don't care how much as they are reimbursed by you when the judges grants approval of the settlement, which normally include the lawyer's bill and his expenses. Double whammy.
Second, the collection of eccie PMs would require LE to have probable cause to get a warrant for eccie servers through a judge and they would have to specify who (associate your RW name and handle) and demonstrate/show probable cause as to why they want/need your records. They may ask back as long as eccie maintains PMs in backup storage. (You are frequently erasing your PMs when you are done communicating with friend? Right.)
May I suggest that hobbyists not keep months of old PMs in their private sent and in-box accounts. What about the person who received your PM--they need to erase the PM also or it remains in their in-box.
But once you erase the PMs, eccie may still have backup archives of PMs--hope not, but I have no idea how long those might be available. It is more likely that there are backups available for current PM that have not erased and maybe some for some that have been erased. Again LE or an lawyer would have to be able to associate your RW name and handle. Companies may also ask LE for reasonable costs, so this usually means an important case, not a fishing expedition.
Finally, the collection of text messages would require LE or a lawyer to have probable cause to obtain a warrant for your cell phone carrier's text message records. Text message records are normally available for each and every msg to/from your phone and will also include text message content as well as message detail information. These records and text messages may be available for 60 days or longer as normal business records needed for billing questions.
In my opinion, these text messages are the most risky of all, since they are available for LE and divorce lawyers to go back and review, long after they have established probable cause to obtain the message content. All they need is your phone number associated with your handle. It does no good to erase your text messages as the original messages are retained on the cell phone carrier's system for at least 60 days.
Most carriers limit and erase records as soon as possible and only keep records for 60 days required by government regulations. It is very expensive for phone companies to maintain large (Petabytes of data) data bases with records on line when they no longer need. There may also be tape/disk storage maintained off line. When the carriers maintain these backup records, they are more liable when responding to legal demands from LE and others. Their risk mitigation strategy is to strictly maintain only that required by law.
Think about the recent concerns of the privacy advocates and civil libertarians in the press with respect to possible government snooping of these types of records for national security purposes--this is the largest "huge data" challenge available--do you think we have some national security agencies able to meet that challenge? Many do.
If you wonder how I know this, I used to work for a phone company and had to deal with legal demands and subpoenas on a daily basis. Most were for voice call-detail records, emails and text message content. Yes, email providers also have to keep email records to respond to legal demands.
If anyone can link your hobby phone number, or your hobby email or PMs to any part of your real world identity, it is then becomes easy to cross-line more info and then to your credit card records, toll road travel, property records, medical, arrests, convictions, etc. We have long digital footprints which are most almost impossible to erase.
If you are still reading, thanks for hanging in there. I hope my opinions and observations are useful and informative about protecting your digital identity and personal information in all environments.