It used to be that you were pretty much anonymous on the Internet if you chose to be, but those halcyon days are now gone, and you should think about whether it's safe to post something online many times over.

Take dating sites for example. Are you absolutely certain that once you've deleted your profile on one of them your information and your photos are deleted forever? Unfortunately, the answer is no.

"Dating sites have an impetus for maintaining your information—what if things don’t work out and you want to reactivate your profile in a few months?" points out Rainey Reitman of the Electronic Frontier Foundation and says that apart from the information being stored on company servers indefinitely - and thus being subject to future legal requests - there is also a high possibility of your photos being permanently hosted on an outside company's servers such as those of Content Delivery Networks, which are often used by many big websites.

Sadly, you aren't safe from that even if the dating website has a privacy policy that guarantees everything you share with it will be deleted when you want it to be so, since privacy policies often change with time. The only thing you can do is to try and make it harder for the website to identify you.

"Get a throw-away email address, avoid using your name, and avoid paid sites that would elicit your credit card number and billing information. To maintain the highest levels of privacy, consider taking steps to obfuscate your IP address, such as using a VPN," advises Reitman.

You should also stop using mobile dating sites that have security holes - such as Grindr - that they have acknowledged but haven't fixed yet.

Furthermore, check carefully the privacy settings of your dating profile and set them so that your profile is not made searchable by search engines - as, for example, an OkCupid profile is by default.

Another thing you must keep in mind is the fact that every photo you post online can be easily linked to you if it's accompanied by correct information, so consider using a pseudonym and fill out some inaccurate information on your dating profile.

"If you use a photo on your dating site that can be associated with one of your other online accounts—for example, if it had previously been shared on your Facebook profile or LinkedIn profile – then your real identity could be easily discovered," adds Reitman. "Before uploading a photo, consider whether you’ve used it in other contexts. Try searching for the image using TinEye and Google Image Search before uploading it. And be aware that search technology and facial recognition technology is rapidly evolving."

Also good to know is that many popular dating sites have trouble with implementing HTTPS, so your login information - and consequently your profile information - can be exposed to attackers, especially since Firesheep was developed. Fortunately, the answer to that problem is easy: use HTTPS Everywhere, a Firefox extension created by the EFF and the Tor Project which forces HTTPS on any URL.

Lastly, you should be aware that many dating sites share your private data with online marketers. They claim it's anonymized, but it has been proven that it is hard to do it properly. If you are concerned about that, you should think about whether you really need to open a profile on that particular site.