It is recommened for all the Vaishnavas to avoid nama-apradhas as much as possible. These are as follows:
From Padma Purana, Brahma Khanda
1)”satam ninda namnah paramam aparadham vitanute
yatah khyatim yatam katham u sahate tad-vigarham”
To blaspheme or criticize the krsna devotees, who have dedicated their lives to chanting the holy name of the Lord.
The holy name, who is identical with Krsna, will never tolerate such blasphemous activities. Such persons will have to undergo the reactions of there offenses.
2) “sivasya sri-visnorya iha guna-namadi-sakalam
dhiya bhinnam pasyet sa khalu hari-nama ahita-karah”
To treat the names and gunas of Supreme Lord Hari equal to the names of other devatas, like Lord Siva (Sivasya Sri Visnorya) - This is second namapradha.
3) “guror avajna”
To disobey the orders of the spiritual master or to consider him an ordinary person.
To blaspheme the Vedic literatures and literatures in pursuance of the Vedic version (puranas etc) as unauthentic.
To think that the holy name is no doubt glorious, but the puranas actually exaggarate it, meaning it is not so glorious as to wipe off all the sins committed by a person in all lifetimes just by chanting a single name.
6) “hari-namni kalpanam”
To consider the glories of the holy name of the Lord as imagination.
7) “namno balad yasya hi papa-buddhir
na vidyate tasya yamair hi suddhih”
(While chanting of the holy name of the Lord can counteract all the past sinful reactions but it is greatest offense to commit sinful activities on the strength of chanting the holy name of the Lord.) To think that the Hare Krsna mantra can counteract all sinful reactions and one may therefore go on with his sinful activities and at the same time chant the Hare Krsna mantra to neutralize them is the greatest offense at the lotus feet of Hari-nama.
subha-kriya-samyam api pramadah”
To consider the chanting of the Hare Krisna maha-mantra to be one of the auspicious ritualistic mantras mentioned in the Vedas as fruitive activity.
9) “asraddadhane vimukhe ’py asrnvati
yas copadesah siva-namaparadhah”
It is an offense to preach the glories of the holy name of the Lord to the faithless.
10) “srute ’pi nama-mahatmye yah priti-rahito narah
aham-mamadi-paramo namni so ’py aparadha-krt”
If one has heard the glories of the transcendental holy name of the Lord but nevertheless continues in a materialistic concept of life, thinking “I am this body and everything belonging to this body is mine [aham mameti],” and does not show respect and love for the chanting of the Hare Krsna maha-mantra, that is an offense.